Egg shells are permeable and oxygen exchange does occur through the shell, that's how it got oxygen for the first 20 days of life. In addition, since it hasn't piped on it's own, it still has it's "placenta" of sorts, forgot the real name, which can do oxygen exchange for the chick. This is why when you peel membrane back, it can bleed. It is still attached to the chick and giving it oxygen. Curled up in the egg like that is hard on the birds ability to breathe so when it feels right or when it's natural membrane starts to go in the chick, it will decide to pip and pop out. Now that you have a hole in the air sac though, don't open the bator anymore as you don't want it to dry out and then the chick will really be stuck. Humidity is now key to your hatch. Good luck!