Theres a small chance that it could be testicular tortion, which can be fixed by a minor operation, I've had it before. If it is then you want to seek medical advice asap as it can be very serious if untreated.
Hi vini, I'm not a doctor, but it sounds like you might have epididymitis, which is where the tube that connects to the testicle gets inflamed. It's not a big deal, but I bet it's causing you tremendous amount of pain. Just go to the doctor and he'll prescribe you medicine to cure it.
Is your testicle swollen at all?