That's what this site was made for. Asking questions helps us learn and avoid making grave errors.
Since the bruising is on the narrow end the baby is most likely malpositioned and won't be able to pip into the aircell. I would make a teeny tiny pin sized safety hole in the middle of the bruising. Very carefully make a small tear through the membrane so that the duckling can start receiving oxygen. Be careful not to go too hard or you will accidently prick the baby. Chicks that have pipped on the wrong side of the egg can usually hatch on their own, but I would keep an eye on it in case you need to assist further. Read the 
Guide to Assisted Hatching and keep us updated on how things are going.