I would take him to your Vet immediately. The Boxer could've damaged or bruised his insides somehow. If the vet says he is ok, ask his opinion. Schnauzers are funny little dogs - once they are afraid of something, it is hard to break them of it. If he is truely afraid of outside, let him out without the other dogs. Then slowly (over several wks. ) add the other dog, for only a few min at a time. But I would take him to your Vet first.
