While nostril asymmetry is the most difficult area of asymmetry to correct, in most cases it can be improved during rhinoplasty. While perfect symmetry is not attainable, improved symmetry usually is.
Nostril asymmetry after rhinoplasty is unfortunately a fairly common problem. It may be related to uneven scarring, asymmetric cartilage suturing, asymmetric graft placement, or persistently deviated septum. It is very hard to determine the exact reason based just on the photos. It is possible that the caudal aspect of your septum is still slightly deviated to the right thus creating this asymmetry. Your surgeon is better aware of the nuances of your surgery and may have better idea as to the reason of your asymmetry. The correction is possible, but usually not straightforward. And there is never a 100% guarantee that the nostrils will be totally symmetric- unfortunately medicine is not an exact science. I suggest you voice your concerns with your primary surgeon one more time, and if the answer doesn't fully satisfactory consider getting a consultation for another rhinoplasty surgeon.
It appears that you are the type of patient that has a good deal of scar tissue with surgery. SOmetimes this can be very frustrating for both the patient and the surgeon as well. I would see out a member of the Rhinoplasty society in your area. A second opinion is always helpful. Sometimes another surgery may be necessary. Good Luck.