Title says it all. Let’s hear your story.
I’ve had a stomach flu 3-4 times in my life. The first time I had it, I wasn’t sure if there was anything a doctor could do and I got it over the weekend so no doc to call. I finally talked to the office on a Monday and they said they could get me some anti-diarrhea meds but that was all. I couldn’t make it anywhere to get the prescription anyway so I didn’t bother.
After that time, some 15 years ago, the next times I’ve had it I just let it run its course. It’s violent, messy, miserable and feels like it will never end. But expelling your insides out both ends and having a fever is actually what cures you. No need to put an early stop to it.
Broken toe, hairline fracture of my coccyx, and a finger injury thanks to not using the guard on the mandoline that should have been stitched. No, not all at the same time.
That would have been a bad day.
I’ve told the story several times, but the worst one I didn’t seek medical attention for (barring some electrical shocks (my fault)) was when I blew off some liquid propane on to my hand. Intensely painful, my hand hurt like hell and was numb for about an hour. I really, truly thought I had frost bite and until the feeling starting coming back wondered if I should get myself to the ER.
Broken toes ( nothing they can really do for you on that), bruised or broken rib.
Pleurisy. A cold worked its way into the lungs and then the pleura (outer lining of the lungs.) Hurt like all hades. Coughing was torture.
But, hey, I was young, I was tough, so I just rode it out, the way you ride out any nasty cold. A couple days and it got better.
I wouldn’t do that today. (More than twice the age!)
Just FTR, for work injuries, Worker’s Comp will cover this stuff, you won’t (shouldn’t) even see a bill and they’ll pay you for lost time if it’s more than certain amount of time off. Plus, for certain things there’s a cash settlement at the end so you’ll get cash.
Now, I’m not advocating people cheating the system, but doing something at work that results in an injury (totally your fault or not) is always worth getting checked out, there’s just no good reason not to. If for no other reason, if it turns into something later on you’re not paying for it out of pocket because you didn’t report it (and see someone) when it happened.
At least this is the case in Wisconsin where Worker’s Comp is mandated by law. Yes, it sucks that their rates will go up because you tripped over a piece of lettuce (shut up) and cost them [worker’s comp] $90,000 (yes, really), but it’s better than you paying for it out of pocket when 2 years later you decide you can’t deal with the pain anymore (I tore my shoulder). On top of that, if you go to a doctor later on and say the magic words ‘it happened at work’ your insurance company may deny payment on it and you might have to jump through some hoops to get WC to pay for it since you didn’t report it when it happened.
Cut the bejeezus out of my hand while at a party. We had all been drinking, so I didn’t go to the ER. I saw my regular doc a few days later to see if he could wrap or stitch it (it was in a location difficult to bandage) and he wanted to know why the hell I hadn’t been to the ER.
Broken toe.
A kidney stone. The renal colic was painful, but not awful. I’ve had them before, and was peeing fine and didn’t have a high fever. I already have percocet in the house. So I just took the percocet, drank a lot of water, and used a heating pad. Worked fine. (I probably should’ve gone to the ER with that one.)
Broken L wrist - just throwing a sloppy hook to a thai pad. Continued training/fighting for a couple of years after - just wrapped it. Was a real quick tap out when anyone went after that arm! 
I eventually got it x-rayed when I was having some problems with my foot, and the doctor showed me the bone chips. The x-rays were enough to convince me that at my age my martial arts days were over. I remember asking the doctor if I could golf with it as it was. He said I could do whatever I wanted, it was already broken. (Doctors seem not to be too terribly sympathetic when you come in with martial arts related injuries! ;)) Doc said the only thing to do was surgery, but it didn’t interfere with my golf swing so I never got around to it.
I fell backwards into a piece of glass and sliced open my elbow to the bone. The cut was about 2 inches long. I pulled it back together with several butterfly bandages. It healed well, but left a nice scar.
I also fell backwards over a baby gate and broke my left arm. It took about 10 months before I was able to fully straighten it again. I am assuming it was broken by the color and odd way it looked.
When I was a kid I shimmied up a rusty pipe that was holding up an upstairs porch. I slid back down and cut my stomach open on a bolt that was sticking out. I’m amazed I didn’t get sick from that one.
I banged my left middle toe on something so bad that it was pointing to the left. I had my ex-husband yank it back into place.
The first and second ones happened while drinking. I don’t drink anymore.
I remember as a kid having Strep Throat (at least that is what my Mom told me). All I remember is my parents worrying when the thermometer registered 105F. Covered me in cold towels, IIRC, until it came down to only 102F. No doctor visit.
Also as a kid, jumped off a wall and tore a chunk of flesh out of my knee. Mom washed some scissors, nipped it off, and bandaged it, all without see a doctor (still have the scar to show for it.)
Ignored gallstones until the pain got so bad I could literally not sleep at night.
Since I hit 55, I have been slightly more interested in my healt.
E. coli poisoning. (Or, I’m 99% sure it was e. coli poisoning, since, you know, I didn’t go to the doctor to confirm.) I sure had the tell-tale symptoms, though, gah!
That reminds me: this doesn’t entirely fit the bill but… When I was 11 years old, I had a severe case of food poisoning that lasted over two weeks before I could eat anything without vomiting or diarrhea. Unlike every other food-borne illness I’ve ever had, it began with a fever (not stomach problems) and the fever lasted for many days. For the first week or so, I couldn’t keep anything down (even water) and got the dry heaves, and was so weak I couldn’t get out of bed even to use the bathroom when it was necessary. 
My family and I were on vacation in Spain, and both of my parents are fluent in Spanish, but for some reason they waited for days before taking me to a medical clinic. The doctor there just prodded my stomach a bit and told my parents to make me drink lemonade with baking soda in it. That was it.
So, yes, I did get medical attention, but it was woefully inadequate. (And, no surprise, I couldn’t keep the lemonade down, either, so that was useless.)
At some point I noticed that when I pushed the skin on the back of my hand around and let go, my skin would stay in that position – what I learned years later was a sign of moderate to severe dehydration. I also lost so much weight in just 2 weeks that my shorts would fall right off me unless the waistband was pinned. Looking back, I think I’m lucky I survived.
(And I still scratch my head a little at why my parents didn’t pursue better medical care for me. They even continued traveling on their planned itinerary like everything was normal, just leaving me in the car or hotel since I was too weak to walk around with them! Not their best moments of parenting, to say the least.)
E: And I still don’t know what illness I had! We assume it was food poisoning, but maybe it was cholera or something, who knows??
(Ok, it probably wasn’t cholera. :p)
Broke my left ring finger wrestling during my senior year in high school.
Didn’t want to miss any practices or meets, so I didn’t tell my parents. I just taped it to the next finger when I wrestled and treated it gingerly the rest of the time. It was fine in a month or two.
It’s still crooked today. 
Broken wrist.
A few days before Christmas one year I was on the way to the company Christmas party which was being held at a fancy hotel. I slipped and fell with my full weight flat on my left hand. Hurt like hell, but I assumed it was a sprain, so I carried on through dinner. The pain did subside somewhat, but I couldn’t move it very well and it didn’t seem to be getting better, so a couple of weeks later I went to the doctor and had x-rays. He said it was a punch(?) fracture and that the only way (after so much time) for it to heal properly was to re-break it so it could be set. The alternative was physical therapy to restore as much range of motion as possible. I picked option B. Those guys were great, and I hardly ever notice it any more. Once in a while it aches a little, and my left wrist bone protrudes a little more than the right one, but it’s almost like it never happened.
I did that. Not wrestling, but during a basketball game. Can’t remember if I was a senior or a junior. And mine is still crooked too. Wasn’t the ring finger, though, but the second finger. It looks weird when I give someone the finger now.
Worst? Just a year ago. I broke my arm in a fall, just below the elbow. It hurt, but it didn’t look crooked or anything. And then it started to swell, so I put some ice and an ace bandage on. Didn’t help, so after a couple of days I went to see the doctor. She said it was broken. An x-ray confirmed that. I left with a cast on my arm.
Several concussions (that might explain some things about me), broken toes and fingers, what turned out to be a torn ICL years later, several small but severe burns. Not really major stuff. There are a bunch of things I should have sought treatment for sooner.
Broke a couple of toes. They don’t do much about them so I just taped them up and wore stiff shoes. The worse part was that it was 3 days before a half marathon that I’d already paid for and had trained for quite a bit.
I wasn’t going to see a doctor for what turned out to be a heart attack. I made the mistake of telling my wife, an RN, the next day and she made me go to the ER.
A cracked rib … she had strong thighs.
Broke a big toe and little finger twice, probably because they were never set the first times. I dislocated my shoulder skiing when I hit ice but I felt it go back in when I sat up so I stayed out. Another fall and I couldn’t have put that arm out.