The quick is the tender part inside a dog’s nail that contains nerves and blood vessels. If you cut the quick, your dog will yelp and, because of the blood vessels inside the quick, begin to bleed. If that happens, don’t panic. There are four primary options for stopping a bleeding quick: using a styptic pencil, using a bar of soap, using potassium permanganate, or, in emergencies, taking the dog to your vet.