I had a crown come off on a weekend recently. I tried putting it back on, but it didn't stay very well, and I didn't want to swallow it, so I just left it off until I got to the dentist on Monday. Everything was fine and the dentist just glued it back on.

I would not put glue on it...that could break or compromise the crown, and they are too expensive to risk.

If you're having pain, I'd call the dentist tonight, or in the morning, and maybe s/he can Rx something to get you through. Mine was not painful, but I realize some might be painful or sensitive. If it's very sensitive, you could try dental wax shaped to cover the stump to protect it from air and temp changes.