Did you put the egg back with her? If so I would get it out and incubate it, the reason why is because her weight will sqoosh it. Ive had it done to many times. It needs to sit in a nice quiet place right now. The egg is now very delicate and can easily be smashed..I just found one of the eggs under my brooder hen cracked pretty well, but membrane is still intact and we are at day 18 today, so I used the advice on this tread and candle waxed it, it took a good bit of wax so I will have to watch it closely to see if it starts pipping and needs help, or can they get though the wax easily? I am not sure when it cracked, could have been as much as 2 days ago since that was the last time I made my broody get off the nest (she wont get up on her own). Fingers crossed!!! The crack was on the side almost touching where the air sac was if that matters. I tried candling it and all I could see was darkness and air sac.
If I keep candling it will I see anything different just before or when it is trying to hatch? Or will I still see a dark mass and separate air sac?
Also if it happened two days ago, your risking bacteria getting inside, so again your best bet is to just incubate that egg, when it hatches if it does, you can always sneek it underneath that momma..