Ingrown hair or growth in groin.

Hi,
I have been reading lots of posts but nothing seems quite the same. I'm hoping someone can help me.

So, I had what I thought was an ingrown hair in my groin. It started off tiny, like 1 pore, growing to a blind pimple, but I've tried digging it out many, many times and never find anything, after near 2 years the tissue feels like its an inch deep, and when it swells gets as big as approx half a ping-pong ball. So sometimes I'll poke it a little to see if there might be any opening, one little squeeze and it will swell up pretty quickly, if I stick a needle it some puss does come out. It doesn't really get sore though. Could this be cancer? Or, Any ideas?
Thanks for your time.