If your dog is bitten by a big dog, you should immediately wash the wound with soap and water for 10 to 15 minutes. Clean the wound thoroughly, then apply iodine on the surface of the wound for disinfection, and then take the dog to the pet hospital. Get a rabies vaccine to prevent your dog from getting rabies. It is best to give your dog regular rabies vaccinations, wear a leash when going out, and stay away from other dogs to avoid bites.