Off-Centered Columella and Uneven Nostrils

It would be helpful to see a more inclusive photo to judge the asymmetry, because it does not appear to fall into the range of “extreme.” That said, to answer your question, your issue likely involves the caudal septum. An in-person examination would be best advised to provide you with the proper diagnosis and plan of action. Keep in mind that no two sides of a nose, face or body are every perfectly symmetrical, so please don’t overanalyze yourself as humans have a tendency to do! I recommend following up with your original surgeon to discuss your concerns and options. You might also wish to consult with a board certified plastic surgeon who specializes in revision rhinoplasty.

At this point you will need a revision rhinoplasty +/- septoplasty to improve the asymmetry - the good news is that there is room for improvement

The best photograph for this problem is the so-called "worm's-eye view" taken with your nose pointing up toward the ceiling. In addition, you did not say whether you had uneven nostrils before your first surgery or if you had nostril reduction surgery at that time.  That being said, usually uneven nostrils is due to a deviated caudal septum.  The best treatment for this is straightening of the caudal septum.  If you had Weir excisions and the alar lobules are uneven, then a revision of the nostril reduction surgery is required.