Probably your son just wants to seek your attention when he hurts himself. According to child psychologists say, the best way is to ignore him when he's hurting himself. You might feel scared when your kid is hurting himself. Unless he's killing himself, you or your family can ignore him. Let him understand it's useless to get your attention by hurting himself. Then, later on, he will stop doing this again.... but be patient. It may take a while.