I have a spot on my leg that is no bigger then a pencil eraser. It feels like a little knot in the middle. Its weird cause I have no pain/itching/swelling in the area. The spot will turn a dark brown kinda purplish color. I kind of noticed little black circles around the edges. At times the color goes completely away and its just the knot and then the dark brown/purple colors appear again. Just when I think its going away it comes back? How could color fade completely and come back dark multiple times?