Is a non-surgical nostril reduction effective in decreasing the width?

There have been described some procedures to narrow the alar base using suture techniques through the skin (percutaneously). Although no significant cutting is taking place, it's arguable whether to call this "non-surgical." it's not a preferred technique since it can sometimes affect the appearance and feel when smiling.
Generally speaking, reduction of wide or flared nostrils is best addressed surgically.
All the best,
--DCP

A Non-Surgical Rhinoplasty is helpful to fill indented areas of the nose. You can have a small profile-bump camouflaged, or a crooked appearance straightened. You can even have imperfections from previous surgery improved.
Fillers will not narrow your tip, or decrease nostril flare with smiling.
I hope this helps, and best regards.

I will follow this question closely.l  I am unaware of any non-surgical procedure to reduce nasal flare or widened nostrils.  Be sure you go to a board certified physician and don't be afraid to ask questions about the success rate, scarring, etc., and ask to see photos.