I had unders and i had the same sort of tender to touch pain. I think i also pulled the muscle from under my left arm by over-reaching as i couldnt put my arm straight up and when i felt it with my right hand the muscle was all tight. I was worried as my left is much higher and firmer than my right, i phoned nurse but she wasnt worried and at 5 wks i started to massage the muscle and its not tender anymore and the muscle isnt as hard to touch, so hopefully my left will drop soon. I saw nurse yesterday for my 6wk check and she said all was ok and asked which i had the problem with as they looked fine to her.
My nurse has always said unless you’ve got an orange and coconut situation, or constant pain, redness, heat, discharge etc then shouldnt be anything to worry about. x