If the swelling is painless, the best bet is a hernia or a hydrocele (a collection of fluid in the scrotum). Since you don't mention pain or tenderness, epididymitis or other infection seems unlikely. In any case, see a health care provider.
HHH, MD
Hi,You need to go and get it checked,it more than likely some type of infection.It sounds like an infection of the Epididymitis.But it would take a checkup to know for sure.Good luck.