Why Do I Have a Dent On My Nostril But Never Had a Nose Job?

Really need a photograph or an examination to understand the extent or type of nasal deformity that you are describing.  Since the nose is made of both cartilage and bone an abnormality of either one could cause a depression.  It is very common to have an injury to the nose and if the cartilage is damaged it tends to bow toward the side of the injury.  So the etiology of the defect may have started years ago.  A rhinoplasty would likely correct the problem.  

A proper examination of both the inside and outside of your nose is recommended to help determine the cause of what you are seeing and to determine how to best improve your nasal appearance.  At the same time, it would be best to evaluate the status of the nasal polyps so that a proper plan can be formed to improve the outward appearance of your nose while allowing you to breathe through the nose.  Please consult with a facial plastic surgeon who can address both the inside and outside of your nose to help you achieve the results you seek.