What Causes A Fluid Filled Blister Between Scrotum And Inner Thigh?

Hello, I m an 18 year old Hispanic male, and recently I ve noticed what looks like some sort of blood blister or giant pimple right between my ball sack and my leg (like if you put a finger right between your nuts and your leg, you can feel what feels like a bone or a tendon right there and it s right on that.) It doesn t hurts whenever I touch it, and doesn t pop or go away like you would expect a pimple or a blood blister to. It s definitely not an STD of any kind, because I ve never had sex. I ve read of a similar thing where it was an ingrown hair, but I ve seen that before and this doesn t seem like that.