I just got my first-ever flu shot @ 39 years old and I just gotta say, well, like I said in the title, owww.
It didn’t hurt immediately, the poke wasn’t even painful. Now though 45 minutes later I have such an ache in my upper right arm. 
If you share a home with someone, go home and whine and demand that they pamper you 'cause you’re hurting. Ice cream is an excellent analgesic, whether applied topically (though that’s a waste of good ice cream) or taken internally. If you don’t share a home with someone, take care of yourself, and remember that means you get to keep all the ice cream, no need to share 
More seriously - I wonder if this year’s is a more pugnacious mix. My arm was sore for a couple of days (that varies from year-to-year; some years, no pain) and I got a hell of a bruise there too. But it’s not unusual to get sore - some inflammatory stuff goes on there because of the foreign germ-like stuff that’s been injected. Ibuprofen is your friend for the next day or so.
Ouch I hate those intramuscular shots. They always feels like somebody punched you in the arm.
Hope you feel better soon
Ooooh.
kisses it all better
The same thing happened to my uncle and 50 years later he died. I’d be careful if I were you.
Go home, take some ibuprofen and like Mama Zappa said, eat some ice cream. You’ll feel better soon. In addition, I’ve found munching on various junk foods of one’s choosing has amazing curative powers in these situations.
I third (or fourth, or whatever) the eating of ice cream, definitely. 
Received my nifty flu shot Friday at 9am (being high risk is kinda cool - I get to budge in line and no one narks to the teacher!). By 6pm I could barely keep my eyes open and every movement of my body ached. My doctor called to find out how I was feeling. When I told her she replied “Oh, that’s a typical side effect. Didn’t the nurse tell you?” Uhhh, NO.
Luckily she did tell me to rest the entire weekend, don’t so anything strenuous. No lawn mowing? Nope. How about scrubbing the floors? Nope. Doc, I lurve you.
I still have a yellowish bruise but the ache has gone away.
And I agree that ice cream is a good cure. Friday night I made a malted and it helped a lot.