Dont know if its the same, but my son had between anus and scrotum under the skin. It didnt hurt him too much and got pretty big. It was an abscess, which had to be surgically drained. Maybe yours is too?
The only thing i can say is that its a form of an STD. im 12 and just learned it in health class. i cant remeber the name of the STD but its a sexually transmited disease through intercourse or even oral sex. hope i helped! :)
-Rheanna
I suggest play it safe and see your doctor