Testicle pain...what is the cause?

Epididymitis/torsion: Testicular pain has many causes 1trauma 2 torsion of the testis 3epididymitis 4orchitis 5i nguinal hernia when in scrotum 6testicular tumor 7kidney stones can sometime give referred pain in testis if you have pain in testis see your doctor asap.

Lots of stuff: There are many things that could cause this but you should be checked for an infection and to make sure that the testicle is not torsed which can be a surgical emergency, http://www.healthline.com/health/testicular-torsion#Overview1