I am glad to hear the pain is gone. However, you should see your doctor or a urologist. If the doctor finds any abnormality, he or she will probably send you for an ultrasound of the scrotum for a better look at both testicles.

Since the pain went away on its own, I would be most concerned that you had a twisting of a testicle. Doctors call this "testicular torsion". Blood supply decreases because the blood vessel gets caught as the testicle rotates around the spermatic cord. The spermatic cord runs from the testicle to the top of the scrotum.

When a man experiences sudden pain in one of the testicles, other possible causes include:

• Infection
  Infection of the testicles or one of the surrounding portions (orchitis or epididymitis) may cause these symptoms. However, I wouldn’t expect the symptoms to get better this quickly. Also, you did not describe any fever or chills, which often occur with an infection.
• Varicocele or spermatocele
  Swelling and tenderness on one side of the scrotum could be from a varicocele or spermatocele. These are fluid collections next to the testicles. They are not cancerous. But sudden pain would be unusual.
• Cancer
  Although cancer of the testicles usually does not include pain, there are some instances where there is some bleeding into the testis that contains a cancer, and that can cause some of your symptoms.

If the pain comes back, treat this as an urgent medical problem and see a doctor as soon as possible, even if it means going to an emergency room.