Over a year ago, I did sets of simple pushups to failure. Had pain the next day at the outer extremity where the pec and shoulder meet, right above the armpit (on both sides).
A year later, the pain is still not totally gone. I haven’t even worked out ever since. That part above the armpit is still tender.
Tenderness increases when extending arm behind body, or when stretching my arms out like in a fly. I don’t know if that’s relevant, but I don’t have any pain with overhead motions.