Can a nonsurgical nose job reduce nostril width?

Excellent question! Yes, filler placed at the tip of the nose can increase projection, the distance the nasal tip comes forward from the face. In some cases, I also place filler at the base of the columella to increase tip rotation, lifting the tip upward. Projecting the tip takes a base view which is more like a semicircle and makes it a bit more triangular. This causes the tip and nostrils to appear narrower and more refined. These are advanced maneuvers requiring an intimate understanding of the anatomy of the nose and its blood supply. Seek a consultation with an experienced rhinoplasty surgeon who also performs a lot of nonsurgical rhinoplasty, to learn about all of your options. My favorite filler for these techniques is Restylane Lyft, and I often see results lasting 2+  years.Best wishes,Dr. Mehta 

Specifically, injectable fillers do not reduce the width of somebody's nostrils. I hope this is helpful. Sincerely, Dr. Joseph

I recommend getting a formal evaluation with a cosmetic dermatologist to go over your desired results. Facial fillers (like Voluma, Restylane, Juvederm) can be used to improve the symmetry of the nose, but surgery would be needed to improve nostrils or overall shape. Best to see an expert. - Dr. Emer

As a rule neither fillers nor neuromodulators like Botox will help a very wide nose. However, under certain circumstances, a couple of droplets injected appropriately into the sides of the wings of the base of the nose can soften the dilator muscles of that region and hence help to narrow the base of the nose. Likewise if there is a bump or hump at the bridge of the nose, injection and straightening of the bridge of the nose with an injectable filler can help to secondarily narrow the lower portion of the nose as a result of the upward pull. Both technqiues are very advanced injection techniques and should not be left to the hands of novice, inexperienced injectors accustomed merely to treating simple smile lines with fillers or for using Botox for the "eleven lines."  Best of luck to you. 

The best way to narrow the nostrils is using a very simple surgical technique called alar wedge excision.   a crescent of nostril skin is cut out where the nostril meets the cheek. The nice thing is that it can be done under local anesthesia and takes less than an hour. It requires minimal recovery and is much cheaper than a full rhinoplasty.

The term "non-surgical nose-job" is a contradiction of terms:  if it's non-surgical, it's not a "nose job" (rhinoplasty).  That being said, like other areas of the face, slight contour changes may be achieved with injectables, laser treatment, and other non-surgical measures.  Generally however the results are not as dramatic, as stable, or as permanent as surgical techniques. They're minor adjustments.   What you're asking for may be possible, but may not be advisable.  The end objective of every aesthetic treatment should be beauty, self-confidence, and your lasting quality of life.  Techniques earn their legitimacy in service of those outcomes.  Many procedures are "possible," many fewer "advisable." 

ANSWER: Yes! Ultimately, you can create narrower nostrils by increasing the tip projection (which changes the shape from oval to tear-drop), widening the columella, or adding bulk to the alar rims. 
However, know that using filler to create smaller appearing nostrils requires a great deal of experience and technical skill. You may be better served with a surgical rhinoplasty depending on your goals and expectations.
Please consult with a surgeon trained in both surgical and nonsurgical rhinoplasty so that you receive an unbiased, expert opinion.
Hope this helps,
Blake Raggio, MD 

There is no non surgical method to reduce nasal width.  Consult with a plastic surgeon to discuss your options and expectations.