Hello and thanks for posting,

Unfortunately, we are not able to suggest a diagnosis, or tell you what it is. You might have some inflammation or infection there, so do make an appointment to see your GP about it soon. Most of the time, there will be a straightforward medical explanation. Testicular cancer is in fact quite rare. But it is important to go and get checked out by a doctor, for peace of mind.

There is some useful information here,

www.nhs.uk/.../

I hope that it gets sorted out soon for you, 

Best wishes,

Vanda