There are techniques in rhinoplasty that can be done to decrease the roundness of the nostril. Usually it entails placing the cartilage as a graft along the rim of the nostril, above the nostril to push it down and sometimes grafts that have both cartilage and skin that are placed inside your nose to push the rim of your nostril. All of these techniques serve to push the rim of the notril down so that they are not rounded and retracted. As you can see below where the label lateral crus is located. Most techniques entail placing the cartilage grafts above or below the lateral crus to push down the nostril margin or rim to correct the retraction and rounding of the nostril.
