Why does my turtle have white bumps on its body? What should I do?

Those appear to be papillomas caused by a turtle-specific herpesvirus. You would need to have Torti examined by your veterinarian or an experienced herp vet to confirm fibropapillomatosis. The "pimples" are actually benign masses. Surgical resection or laser ablation may be an option to prevent larger tumors from interfering with swimming, vision, breathing or eating.