Hard red ,very painful lump on inner thigh ?

The first day I noticed it I thought it was a huge very hard pimple, I poped it and a lot of pus came out. After a day it got very painful ,got bigger, and got red, noe its about the size of a dollar coin. It hurts even if something lightly passes over it. It just looks like a red coin size bump, with a tiny pealing piece of skin in the center..what can this be, and I've had it for about 5 days