My mum and a couple of other oldies I've spoken to all had much worse pain after their booster shots. Can't speak for the others but my Mum had pfizer for all three of her shots and she said she couldn't sleep for a couple of nights and her arm really hurt, after no problems at all with the original two.
I seem to be getting daily text reminders from the NHS telling me to book my booster, I'm not rushing to do so! There doesn't seem to be any opt out. Just like the incessant texts from HMRC telling me to file my tax return