Smoking after a surgical procedure increases the complications that can can occur such as infection and skin necrosis. Smoking causes vasoconstriction of the blood vessels which restricts oxygen delivery to the tissues. In addition, smokers have a higher carbon monoxide component tin their blood stream which also binds to the red blood cells much greater than oxygen does, therefore restricting oxygen delivery to the tissues. It is best to stop smoking for 2-3 weeks before and after any cosmetic surgery.
In short, smoking shrinks down the tiny capillaries that we rely on to get tissues (especially at the skin level) to heal, not to mention it's irritating to the nasal passages, and of course bad for your lungs (especially coming out of anesthesia) and health in general. If you can't quit outright, at least do so for the first 4-6 weeks of healing post-op to optimize your chances (plus you'll probably have better scarring).