Both my sons had them, and one of them had them twice. They are in no pain. As a matter of fact, they instantly feel better because the earaches are gone. If they've had an ongoing issue, sounds may seem very loud to them for awhile, because they've not been hearing well.
You'll need to plug his ears as long as the tubes are in. If he is little, this will probably include bathtime too. My oldest son's doc recommended Silly Putty, and that is what I used. It forms a perfect seal.
It's going to be one hell of a lot worse on you than it is your son.
