Ok I'm kind of scared af right now because I'm afraid this is the start of a tumor but here's the situation. I have a small ball in my left chest three inches below my nipple and close to my armpit. I could feel it just today, 2 days earlier I started feeling this dull, bruise-Like feel in that area of my chest. Any pressure made it hurt. Today I can actually feel it. It's very small but hard. It's not at the surface, it feels pretty deep. It's moveable and is getting more painful, it's a dull pain all around it. Using my left arm at all triggers slight pain. So what could this be? Should I be worried or what?