My brother was at a friends shooting his gun, and then he shot his friends sons gun ( a glock .45) Not long after shooting that gun a few times he started having trouble hearing out of his right ear, he says everything sounds muffled and there's a little ringing, We did a little research online and everything said to wait it out, but it's been 4 days and he says it's either getting worse or not getting any better. He wasn't wearing ear protection (and learned his lesson) I guess my question is, could he have done permanent damage? Should he keep "waiting it out"? Or should he make an appointment with an ear doctor to get it checked out? And what would the doctor be able to do for him?

He needs to see an ear doctor. It is possible that he did permanent damage. As to what the doctor will be able to do, we don't know as we are not doctors. However, I do shoot for hobby and ALWAYS wear hearing protection.