A small amount of gas pneumothorax can be absorbed gradually by itself, while a large amount of pneumothorax is difficult to be absorbed by itself. Consider that your dog should suffer from "subcutaneous emphysema", that is, gas is released into subcutaneous tissue. If the dog is in good condition and can eat and move, there should be no problem. As long as he is given a good rest, he will gradually recover. But I suggest you take it to a regular pet hospital.