I have had this bump on my lower left shoulder for a couple days now. I haven't done anything to that arm and it seemed to have come out of nowhere. There is no skin discoloration, but it is very painful when I move my arm. Also, when I push down on it, it is very soft and feels like its filled with liquid, so the only thing that I could think of is that it is an abscess. I'm really not sure though, but I would like to know what you think because it is painful.