Yeah, I actually had a number of those as I was growing up. If I remember right when I asked the doctor, he said it was just a cist - a calcium deposit on the bone or something like that - and it'll go away in time. Sure enough, it did. I have gotten several in other parts of my body since then, but it always comes in the form of a hard lump on a bone and it always has gone away. If it is indeed calcium, maybe I should consider not drinking as much milk:) Mine were always on the bone, though, so I'm not sure if this is the same thing as what you're experiencing on your muscle.