My 9 year old son has pock marks on his left shoulder/back. he says it hurts to stretch. he has never had chicken pocks.

Too soon to say: Many rashes resemble Chicken Pox in the early stages, & if your child has been vaccinated at 1 & 4-6 yrs of age, he is much less likely to get this. Chickenpox often starts with a fever, headache, sore throat, or stomachache. These symptoms may last for a few days, with fever in the 101°-102°F. The rash changes appearance over several days (small red bumps, blisters, scabbed lesions). See pic.

Skin Rash: Having "pock marks" in a localized area with some degree of pain can occur with a condition called Shingles which can occur in people who have had past infections with Chickenpox. Although your son has "never had chickenpox", Shingles can occur in persons who received the vaccine (3 cases per million doses). Because skin rashes are difficult to diagnose without a look, see your Pediatrician.