Approx. 2 weeks ago I noticed on the back of my leg, almost behind my kneecap, a dark red spot. At first I thought it was black, until I tried to pull it. It appears to be dark dried blood . It almost looks like a skin tag. When I try to pull it off it pulls at my skin as if its attached beneath the surface. I ve tugged at it roughly and it bleeds around it slightly but will not come off. I m wondering if it s something I should have looked at.