Nose infections/diseases

Any piercing can get infected. You may also have an allergy. People can be allergic to nickel (I am!) whereby you can't wear any earrings, studs, etc. unless they are 24 carat gold. Yep, that's a lot more expensive than 18 carat. Or you could be allergic to latex gloves worn by the piercing technician.

Ask your doctor if you're having breathing problems, that could be a sign of a lot of things, some of which are rather bad. Feel better soon!