I concerened about my cat.

I have a white domestic short hair cat named Tryxie.

Lately, she's been getting black crusty's in one of her nostrils as well as eye boogers I'd call them.

I remove them with a wet Q-tip but it always comes back and just a while ago for the first time I heard my cat sneeze.

What's wrong with her? 

Since the eye boogers and crusties are new, she most likely has airborne allergens, just like a human.  As long as the discharge (nasal or eye) is clear, she's fine.  If the discharge becomes discolored (green, yellow, or some combination), then she needs to go to the vet.