The last few days I've had some tenderness in my left armpit. Today I was in front of a mirror with my arm above my head looking to see if I could see anything. I couldn't see anything in my armpit but there is a little dent in the bottom of my left breast. It disappears when I put my arm down. There's no tenderness or pain in the breast and I can't feel a lump at all. I have previously had benign cysts diagnosed. Any suggestions?