Q. I heard a couple guys in the gym talking about why a boxer shouldn't blow their nose during the fight. Sounded like the silliest thing in the world to me, but it seemed like the most obvious thing in the world to them. Especially as we get to the winter, I get runny noses while sparring all the time. Am I going to explode my head if I blow it?
A. If a boxer has a fractured orbit or a select few other facial bones, blowing your nose can force snot, blood, bacteria and air through the fracture (assuming it communicates with the nasal sinuses) under the skin or worse into the cranial cavity. this can be potentially life threatening. Frankly, blowing your nose in general is rather unhealthy as you can force material into your middle ear quite easily.
The condition is called "subcutaneous emphysema" or air under the skin.
In case you missed it earlier, Doc Dill isn't actually a doctor. Take his advice for what it's worth, but consider talking to someone with the appropriate credentials.