Abdominal injuries can occur from car accidents, falls, or even an accidental kick to the stomach from a human or horse. A dog in pain might bite, hunch its back and/or refuse to move. Even if you cannot see outward signs of injury, there may be damage to internal organs and therefore it is important that you seek veterinary attention. If your dog does not have a severe injury and is not in serious pain you can try treating him at home otherwise you will have to take him to the vet.