A: Keep the wound clean, change the bandage three times a day, avoid working with your hand for a few weeks. If you follow those simple steps, your nail will be back to normal before you know it.
But, when it comes to nail care, the best treatment is prevention. In the future, when you turn into a werewolf, you might consider staying at home to enjoy a quiet night by yourself, instead of running into town, terrorizing villagers, mauling everyone you see with your razor sharp claws. The villagers have are aware of your transformation cycle. They've been paying attention. They can know when the moon will be full, giving them ample lead time to construct replica villagers made out of stone. Those stone villagers can be murder on your nails.