You don't need to worry about the air cell if you left a little bit of air in with the egg. Bacterial growth is going to be your biggest worry, that and moving the embryo developing inside. I suggest you tilt your incubator from side to side while incubating: put a book under one side and then the other, to make sure it doesn't get too jostled around. The chalazae (?spelling) - the white cords inside the egg white - help keep everything in place inside the egg, and by breaking the shell it has no anti shock system anymore.