when applying pressure to my upper right arm , somewhat close to my arm-pit, I can sometimes feel a small ball type shape that is sore to touch but not all of the time. I noticed it last night when I got back from the gym. When I put my arm down I felt something rubbing against my side. It is more annoying than painful, and the only thing I could guess is a pulled muscle, pinched nerve or something along those lines. It is not a major lump, but my friend said that she could definitely feel a difference compared to my other arm.