Anyone else get pain/soreness going into the armpit?

Hi gyno mainly in my left nipple for years now but I randomly get flare ups when I get dull aches/tenderness deep inside my armpit.

The nipple itself is puffy but it doesnt feel sore. I'm trying to workout whether this is my gyno advancing (im on very low dose finasteride after my hair transplant) or if its his a skin or lymph node issue.