Inside Forearm swelling and hand numbness

My 17 year old son had to be yanked in the 2nd when he lost the ability to locate. He throws hard, 85-9 mph. fbs and and curves. On his pitching inside forearm about 3 inches above the wrist a lump spanning 180 degrees of the arm has developed and he says he lost feeling in his hand: “I really didn’t know where the balls were going to go…” The feeling is back now, and the swelling/lump is down a bit (3 hours later). Never read about or experienced such an injury. Help please.

Don’t know what caused the swelling but the symptoms are consistent with a median nerve compression. See a doctor.