For a couple of months now I have noticed a few black and blue spots on my thighs, about five in all. I paid no attention because they never really hurt too much. However, I just realised that a particular area on my upper right thigh is darker than usual. It itches slightly and feels a bit sore. It is one of those marks that I saw months ago, but bigger, about the size of a silver dollar. Anything to worry about?