Why Do We Call it Candling?
Looks a bit like the moon. Bumpy shells often indicate some nutritional imbalance, or other form of stress on the bird that produced the egg. This would indicate that the egg may also not have the nutrition it needs to grow into a healthy duckling. If you are not especially short on eggs, don't use this one for hatching.
Bumby shells don't necessarily mean the egg is not edible. Bumpy shells are also often thinner than normal-shelled eggs. They will loose moisture faster - which may also be a problem for the developing emryo - especially at hatch time.

These eggs are also likely to be more fragile. They're just not a good risk.