If you have an antibiotic ointment (the kind without pain reliever in it), you could apply it to the wound after cleaning it. Coconut oil has antimicrobial properties, so that may be an option, and honey also has wound healing properties (i.e., anti-inflammatory, antibacterial).
There other wound healing sprays on the market, too, so you might be able to find something else locally.
I haven't used turmeric topically on waterfowl, but this
article has some info you may find interesting. If nothing else, cleaning the wound, keeping it dry, keeping the drake away from her, and keeping her healthy (you could offer a vitamin supplement like Nutri-Drench if you have it) should help her heal.
Getting a few more ducks may help relieve the breeding pressure. Is she his favorite? Does the other duck show any signs of breeding stress, like missing feathers?