I am a 46 year old woman. I have just found a lump on my left collar bone. The lump is a little sore. It is half way between the center of my chest and my sholder. It is about the size of a golfball. It feels like it is right on the collar bone. I am a diabetic and just recently got over being sick. I don't feel like this is in my throat or my breast. It is right on the bone. What could it be?