He's allowed to tell you when it hurts, even if he doesn't want to tell the doctor. If he doesn't tell you the second it starts to hurt, by the time he breaks down and asks for the drugs it'll be a half-hour at least 'til he gets some relief. As the dentist told me after chipping out a piece of my jaw to remove a wisdom tooth: "By the time you feel the pain, it's too late to take the pill."
Good luck.