I recently got a tetanus shot.
Literally didn't feel it, I remember seeing them mess with some paper, pull out a needle, and I don't really like getting shots so I didn't look, I only turned around when I heard the door open as the nurse walked out of the room.
Virtually painless, it sort of bruised up a few hours later, but was not a problem at all really, maybe I just got lucky, who knows, but I wouldn't worry about it.