Will fillers fix nasal sidewall collapse?

A deviated septum can cause breathing issues. The septum goes all the way to the top or bridge of the nose. Crookedness in this area will cause a dent or curvature of the nose. Filler can camouflage this sometimes. Also weak cartilages can collapse in from the sides of the nose or nasal tip. Again, these might be partially camouflaged by filler, but a more definitive treatment would be through septoplasty (for breathing) and rhinoplasty (to straighten and support the external nasal structures(.

When you breathe through the nose, does the sidewall collapse get worse? If that is the case, then filler likely will not help. It doesn't provide any structure to the nose. It could potentially help with the appearance of the indentation on that side, but if the concern is breathing well through that nostril, then it could also make it worse by causing the sidewall to bulge into the nasal cavity. If you are concerned only about appearance and if your breathing is normal without any dynamic collapse (collapsing during inspiration), then it could improve the appearance. If the concern is with breathing and not appearance, and you want to avoid surgery, we have a couple minimally invasive options that may be effective for you for treating the nasal valve collapse.
You can check out the link below for more information on a nonsurgical rhinoplasty.