Some sources of testicular pain are emergencies, and failing to seek immediate treatment may result in losing a testicle. This is the case with testicular torsion.
A strong force of torque is great when discussing a truck engine, but less so when discussing forces inside your scrotum. Ideally, your scrotum is a torque-free zone. Sometimes, however, the spermatic cord gets twisted and shuts off blood flow to your testicles.
The name sounds painful, and it is. You'll feel it in one testicle or the other, and you probably couldn't ignore this kind of agony even if you tried. And you wouldn't want to -- leaving it untreated could result in the loss of the affected testicle. The pain is a clear and definite sign that something is terribly wrong. You'll need surgery, and fast.
If the testicle can be saved, it will be re-set and then stitched to the inside of your scrotum to prevent future twisting. A follow-up procedure will do the same for your other testicle. This doesn't sound so great for a best-case scenario, but after experiencing the pain of testicular torsion, you'll welcome a helpful and simple sew-job to prevent it from happening again.