Can I occasionally smoke a couple of weeks after rhinoplasty?

Smoking cigarettes before or after your surgery can delay healing and increase risk of complications.  I recommend you continue to avoid smoking until you are completely healed.  You should contact your surgeon to discuss when you may resume. 

While it's not recommended and may delay overall healing, infrequent smoking three weeks after rhinoplasty surgery should not have a huge impact on your nose.

Although smoking is discouraged due to the negative impact it has on blood flow to an operative field, the nose has such good vascular supply, that smoking is unlikely to have any impact on your nasal surgery. That said, smoking does not help healing, and if you have had an open rhinoplasty with an incision across your columella then you have to be more cautious because some of the vessels that go to your tip may be compromised and further constriction of blood flow due to the nicotine may challenge the skin of the tip or the incision as well. Be careful. After six weeks, it wont matter for sure. You should make this an opportunity to quit all together. New nose, new lifestyle.