Really hope you can help, as am pretty worried...

I am 24 years of age and a healthy male- always at the gym and keep fit. My diet is very good too and varied- a lot of oily fish etc

Last week, I discovered a hard lump underneath my skin on my perinium (between the anus and testicles). It is closer to the anus (about 3-4cm from there I guess) than to the testicles and I can only feel it if I apply a fair bit of pressure as it is internal. It is totally painless and is only small in size (like a pea)...

Could anybody possibly help me??