I had this same problem for the first time last night and was extremely freaked out (I almost couldn't sleep). I was just coming off of my period, and just the tiniest bit of friction seemed to do it in my case...
I've had "dry" sex and friction before and haven't had this issue.
Needless to say, it's nice to know I'm not alone (or a freak of nature).
But I'm not sure that if you have this, it's always going to need an operation. In the morning, the swelling had gone down slightly. I took a hot bath to try to ease the remaining inflammation, and then took an ibuprofen tablet. It seems to have done the trick, because it's almost back to normal. No operation needed every time, I think.
I hope this doesn't keep happening, and I can't say that it won't get more serious.