My friend is cutting himself

I dont know where to post this but my best friend is one of the funniest people alive and is always happy and i suspected he had depression which i still dont know if hes hiding or if he doesnt have, today on the gp he talked about how when he gets mad he scratched himself until it hurts and sometimes also beats himself and i just dont know what to do he says his problems are stupid and doesnt want to worry his friends.

Can Anyone help me i dont know what to do or what to say.