Probably not; it's probably a birth mark or age spot of some kind; but if it changes, thickens, gets bigger or darker, etc, go to a dermatologist.

I bet I've got you beat anyway. I have a very large brown birth mark (I'm also pale) on my left inner thigh, coming right out of my groin. It's about three inches in diameter. It shows in nearly anything short. bathing suits, cute shorts, etc. I was on swim team anyway, despite the fact that I look like I have a blob of crap down there. It's all about being confident in yourself.