I had this! Third day after my second Pfizer dose. I am very familiar with chest pains through... recreation... and this was a whole nother beast. I was legitimately frightened, even moreso when everything I found said it wasn't a symptom and shouldn't be happening. I did find a 3 month old (at the time) Reddit thread where several other people had commented in the last 24 hours saying they'd found it the same way (maybe a google algorithm effect?).
It cleared up after three days, getting better each day. 34 year old male with no other side effects from either dose.