I can say one thing is harmful, since the pressure goes to the head and the droppers burst before our eyes, he sneezed and did not notice anything alive) just the doctor saw it once and explained, you just need to cover the company)
I always pinch my nose when I sneeze, so as not to annoy others with unnecessary sounds. I did not notice anything supernatural. Not even a hint of tissue tears or any other complications.
I'll try to assume that no ... firstly, sneezes go not only through the nose, but also through the mouth ... The sneeze speed is approximately 4-5 m / s, with a small volume of air, you can sneeze without even letting out air from yourself, with a large volume, most likely you will not be able to hold back the air with your lips. If, nevertheless, you manage to somehow tightly clog both your nose and mouth, then most likely your cheeks and soft tissues of the mouth and throat cavity will swell greatly, in the worst case, these tissues can tear and in the absence of timely medical assistance, you can die from hemorrhage ...