Significant unevenness in my nostrils after rhinoplasty. How can this be treated?

Asymmetry of the nostrils, by itself, can be very difficult to fix. However, if there is a bump, too, and the tip has fallen, then those two issues should be addressed at the same time as looking at the nostrils. Hard to say what's causing the breathing problem, without having the chance to look *inside* the nose, but also, just elevating the tip of a nose can, by itself, help with the breathing.

If your tip is too low, I would suggest against *only* a rasping of the dorsum. Lowering a bump without raising the tip usually makes a nose look longer, as if the tip had fallen more, and you probably wouldn't like that very much.