Put a dab of glue on your finger tip, elmer's glue, gorilla glue,etc.
Smear it on the crack, just skim coat it, and don't get it all over the place, just seal the crack. Let it dry and put it back .
Check on it in a few days and sniff it the egg. If it smells rotten (you'll know!) chuck it.
Good luck. I had a dented and crack egg hatch doing this.