If Timmy was punched hard enough, he can have fractures on the cartilage structure of the throat, since the cartilage is flexible and not as strong as the bones. If damage is inflicted, by strong hit for example, on the larynx, it begins to swell. If it swells too much, the flow of air can blocked and you start to suffocate. How would this affect his respiratory system? Timmy’s cartilage plates around the larynx are probably severely damaged and this can compromise the airways and let the air to escape into his neck and chest. The trachea could be further damaged and as well as the esophagus. If in the moment of the punch he had breathed in, the air he had inhaled can’t escape through its normal way. That’s why it will find another way out.