First, you should never try to diagnose your son's medical issues and he should not be guessing what it might be. If something hurts and is uncomfortable he should not be doing certain activities, example lifting or batting practice. It could be a number of things and the ortho should be one who treats sports injuries.
When DK was in AA his fingers tingled. It wasn't painful just annoying. He went to see team surgeon in STL after season ended and had an EMG with a neurologist, the diagnosis was actually correct that he needed surgery to move ulnar nerve from the groove in elbow to the side, but he opted to go back to the doctor in NY (NYM) who had done surgery a few years before on another issue. Ulnar nerve repositioning is not uncommon but needs a neurologist to aid in the diagnosis. In sons case the nerve had to be moved asap.
He had surgery that November and was still struggling in spring training, because while surgeon was moving the nerve, he had an elbow cleanup. That hurt! It took about 6-7 months before he felt almost normal.
TPM