I think you should see a doctor as soon as possible. I don't know of any home remedies for testical pain or any easily fixed problems that can cause testical pain. Since you didn't mention any injury to the area, I will assume that is not the cause of your pain.

Testicle pain can be caused by many things and may come from testicular disorders or pain from somewhere else in the groin. They may include:

Chlamydia
Epididymitis (testicle inflammation)
Hydrocele (swelling of the scrotum)
Inguinal hernia
Kidney stones
Mumps
Orchitis (inflamed testicle)
Retractile testicle (a testicle that pulls up inside the groin — this condition occurs in young boys)
Scrotal masses
Spermatocele (fluid buildup in the testicle)
Testicle injury or blow to the testicles
Testicular torsion (twisted testicle)
Testicular cancer
Varicocele (enlarged veins in the scrotum)