One nostril sits higher than the other and has more cartilage than the other - makes nose look crooked. What can be done?

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.  

From your description, it sounds like your nose may be asymmetric and would need slight adjustments. I recommend having a non-surgical rhinoplasty or conservative rhinoplasty procedure. A non-surgical rhinoplasty involved injecting temporary fillers in the nose to make the nose look balance. However, it does not reduce the size of the nose. A surgical rhinoplasty can reduce the size of your nose as well as the position of your nostrils. I recommend consulting a board certified facial plastic surgeon in your area about the best treatment for you.

Differences in nostril shape and position can occur due to your underlying nasal tip cartilages and possible asymmetry in the structure and orientation of those cartilages. Rhinoplasty can be performed to improve symmetry and balance of your nose. Based on nasal aesthetics, a rhinoplasty surgeon would need to determine if your left nostril needs to be lowered or if the right nostril needs to be elevated (both of which can be done with various techniques including cartilage grafting and/or repositioning of the cartilage). Good luck!