A stupid near-injury:
I was removing the tin seal on my Coffeemate bottle the only way I know how – with my teeth. Instead of the whole thing coming open, a little piece tore off, just as I inhaled. First thing in the morning without my coffee yet! Luckily my reflexes kicked in and I coughed/expelled it back out. That could have been an embarrassing ER trip.
“Chicken make a BAD pet!”
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I strained my thumb playing my Nintendo 3DS. TWICE.
And I don’t even play anything that active, mostly Pokemon and Sudoku… 
I once nearly dislocated my own thumb while having a gigantic boil lanced sans anesthetic.
Speaking of which, it never occurred to me to name my boils.
I once smashed my hand against a piece of playground equipment as a child, not realizing there was a bee there.
I once ran head-first into a kid and was knocked out for a brief time. I had a ginormous goose-egg on my head for a couple weeks.
I still have a clump of scar tissue in the middle of my forehead from all the times I fell on it as a kid (or when my brother clambered out of the double stroller and flipped my out of it onto my face). :smack:
Played “Frisbee” with a window pane once back in late 70’s…and the long scar in the palm of my left hand marks where I caught it.
geez, didn’t you know it was a scorpion when you started ferrying it across the river?
My sister-in-law was tidying up her apartment before hosting the family for Christmas Eve. While fluffing up the pillows on the couch, she smacked her left hand with her right, and fractured a bone in her left index finger. 25 years later, we still give her grief over that one. 
I’ll contribute my mom’s. She taught for 35 or so years. One year, she got the idea that she needed to scrap the gum off her ceiling. So she stood on top of a desk. You know the ones, where the kids sit one to a desk, there’s a chair, and the desk sits out in front of the chair completely unsupported - kind of like this.
She climbed up on top of the desk, promptly pitched forward onto the floor and ended up with a compound fracture of her forearm. She had a metal frame supporting the injury for a while, and then had surgery, followed by months of physical therapy to regain use of her hand (the nerves were damaged in the break).
Lesson: do not stand on unsupported furniture to do work on your ceiling.
I once pulled a muscle in my shoulder whilst masturbating in the shower.
Did you see a doctor? How did you explain that one? 
I ended up with a painful friction burn on my back from a vigorous sexual encounter on a cheap, nasty pile carpet.
When I was 16 I decided to run a Swiss Army knife blade along the bottom of my right foot…to, uh, see what would happen. The results were what you’d expect.
I caught a pretty good sized catfish and I put my thumb in it’s mouth to show it off and it bit me very very hard.
It hurt for a long time.
Apparently, caution isn’t in her nature.
When I was a kid I put my finger on the top of a gas lantern to see if it was hot. It was.
As an adult I smashed my head really hard into the “please mind your head” sign in the crown of the Statue of Liberty.
Most memorable was playing football in my back yard, about 11-12. Looked back to see if anybody was close and ran into a tree…a big one. Still have the inch-long scar on the side of my head.
Most recently (I’m 63 now), refereed indoor soccer and backed up into a 5-year old. Took a tumble (the kid was just fine, I didn’t fall on them) and strained my back something fierce.
Naw, it healed up in a day or two. But all that day, I had people asking me “What’s wrong?” with a follow-up of “How’d you do that?” I tried a few different tacks, but think I ended up going with, “I dunno, I just woke up and it was messed up.”
Had a 6" long drill bit in my back pocket. Got in my car and adjusted myself to the seat. Drill bit went through my jeans, underwear and left butt cheek. Pulled it out and went on my way. 15 minutes later stopped at an ER, the pain was spreading to my back and leg. I quit carry drill bits in my pocket after that.