My husband has a pain on his left scrotum the pain is only if he touch is it! What can it be?

Pain in the scrotum. Infection of the testis (orchitis) may result in painful testes. A course of antibiotics prescribed by your doctor might help.
Epidydimitis. Pain possible infection in tube starting in testicle needs to see physician.
Epididymitis. Hard to say but could be infection of the sperm gland. He should get evaluated.