I have a lump on my back and not sure who I should see for it. It seems to have grown quickly, due to it's size and having not noticed it before now. It is completely under the skin, pretty hard, but moves when touched. It is a little tender. I first thought to make an appointment with my dermatologist, which I have for tomorrow, but now am thinking that maybe I should just see my general physician since it doesn't actually seem to me a skin issue. Who should I see?