Any idea what this might be? (Photo)

I'm 2 1/2 yrs post reconstruction surgery. High profile, under muscle. This side has been bothering me with pain sometimes, shift in placement, and harder. Now I have this. I have no nipples, no nipple reconstructed. It's not itching. A bit of soreness in armpit muscles. In foreign country right now, not close to doctor. What could this be? It came rather quickly