I had to get a tetanus shot the other day.
There wasn't any great reason for it. All the times I've scraped myself on barbed wire or stepped on a rusty nail or caught myself with a fishing hook never did me any harm. But the doctor just said it, that I should have a tetanus shot.
I forgot that they were painful, as in real painful, and I didn't remember it till the nurse literally asked me which hand I am, as in right-handed. Then it crossed my mind, hmm, this could hurt.
The actual shot doesn't hurt much, it's the aftermath. It's been almost a week and the pain is still there. It was mostly gone, died down completely, then suddenly it flared up again. It actually reminded me of that place in Revelation where the devil is bound a thousand years and then is released for a short time before finally being cast into the Lake of Fire. (Every time I have any trouble that goes away and returns from the same incident it makes me think of this Bible passage. I keep thinking maybe it's a mythological archetype of sorts, that speaks to the coming and going and surprise re-coming of a particular problem...)
I had Grandma with me. She sat in the waiting room. She's lucky, being 104, because they don't give shots to people over 100. The theory as I heard it is that you've already had enough shots to last you, and any shot you get over 100 might kill you, thereby the cure would be worse than the disease. Once you're over 100 you're a graduate to shots, and there's no post-grad work allowed.