Pre-existing condition- insurance won't pay, what can I do?

I need help! My son has individual health insurance, but a rider for a pre-existing condition for congenital fused vertebrae prevents him from seeking medical help for anything related to his back. Where can he go to get relief for the pain? His job does not pay well and he is going to school to become a certified nurse’s assistant. But his back is giving out due to heavy lifting and he needs some physical therapy. The fused vertebra has nothing to do with the pain.