Pain in the testicles and scrotum

From the data you reported (pain in the testicles when husband was little, and still hurting), it cannot be determined for sure what the problem is. It is not quite clear whether there are any structures attached to the testicles that cause the pain (something reported as “the size of a small pea”).

The pain in the testicles might actually be a pain in the scrotum. Please, be aware that there are other structures in the scrotum than the testicles. All of them might be affected and might cause pain. For example, the epididymis is attached on the posterior edge of the testicle where it can be touched and might become inflamed. Inflammation is a common cause for pain in the scrotum. The structures might easily become inflamed if the urine returns from the bladder into the genital ducts.

Your husband might want to visit a urologist for a physical examination and ultrasound of the testicles. If you are worried about the fertility, simple semen analysis might solve all your dilemmas. The pain might be caused by other structures in the scrotum that do not affect fertility at all.