If you can't easily detach it, it's better to let it be. You can however put a bit of anti-fungus powder, like for your feet, on the bad egg to prevent fungus from growing and spreading. An egg with a weaker spot that might survive to hatch could otherwise be infected with the fungus and perish. Prevent the powder from falling on the bedding or other eggs, just dip a cotton tip in a bit of powder and touch the surface of the bad egg with it carefully. Maybe cream can be used for it too, never tried but why not.