My son had soreness on one side of his tongue, which followed a swollen roof of mouth. Now has off and on sore throat and swollen gland on one side.

Evaluation needed. It would be prudent for your son to see a physician to determine the cause of these symptoms and then appropriate treatment if necessary. It could be a viral or bacterial infection or something else. Only a personal clinical examination can accurately determine the cause of these symptoms.
Innfection. Your son may be experiencing some kind of infection, could be a number of things, a wisdom tooth, an infected nerve, an abscess, a tumor, a medical condition.... You need too take him to the dentist for proper evaluation, x-rays and appropriate treatment. Take care.
Infection. He has some sort of infection , either viral of bacteria. In either case he should be seen by a physician.