Red bump on groin

Hi
I'm 16 and a virgin. A few days ago I noticed a flat, round, red bump on my groin a few centimeters above and to the right of my penis. It itches, but not unbearably so -- though I did scratch it raw without really paying attention, in fact that's how I discovered it. Since then I haven't had trouble not itching it. It's about the diameter of a pencil eraser.

I don't know what this is and it's really bugging me; any help would be greatly appreciated.