What To Do For The Spot On The Shoulder?

Hi, I just noticed a red "spot" on my shoulder. It is about 1 cm in dia., very red in color, round and has a very clear boarder. It is not raised, does not itch or hurt. It was not there yesterday. It is very red, at first I thought I spilled something on myself and tried to wash it off, it does not change color if I push on it.