I have a small pea-sized lump on the left base of my scrotum. The lump is not in the scrotum, but right where my left thigh joins with the body. The lump is hard, does not seem to move around, and almost looks like a pimple at the surface of the skin. There is only pain, similar to that of trying to pop a pimple, when I apply pressure on the lump. What can this be?