Matter of fact, the nose switches between which nostril to breathe out of in cycles about four hours long. This switch happens via erectile tissue inside the nose, not unlike the erectile tissue in a penis or clitoris, swelling and blocking one nostril while shrinking and opening the other.
Your body may also react differently depending on which nostril you use. Using the right one may increase your alertness and concentration, while the left might calm you down and reduce stress.
We have two small nostrils instead of one big one for a reason.