I've noticed my nose is crooked. It's most evident when looking at my nostrils from below. They're different sizes. (photo)

Thank you for your photos.  I get this concern quite frequently from patients. We all have some sort of difference in our nostrils when looking at them from underneath.  I recommend you sit down with a plastic surgeon that can walk you through what your options are to correct the asymmetry, and give you honest answers to help meet your expectations on what you want your nose to look like.  You may be a candidate for Rhinoplasty, and Septoplasty which will help give you for symmetry for your face.  Computer imaging with 3D system may help make some decisions. Good luck

Your nose is a symmetrical as they come. If you are otherwise satisfied with the appearance of the nose I would suggest you do nothing surgically.