Smell from nose 4 weeks post-rhinoplasty - but no other symptoms?

It is difficult to say what the exact cause of your smell is from. In many instances, there are raw areas covered by bloody crusts, as may be the case if turbinate surgery was performed, and superficial bacterial colonization may occur under these crusts. Though not of any clinical significance, they may produce a foul odor. Sometimes a sinusitis may result from the initial packing which should be addressed with antibiotics. I have even heard of foreign body reactions taking place in the nose causing odors. It sounds as though you are doing everything correctly . However, I would check back with your surgeon to have him re-evaluate it.

It is not uncommon for you to have an altered sense of smell and taste for several weeks following rhinoplasty.  This usually resolves by 2-3 months.  Relay your concerns to your surgeon and he or she will provide you with a reasonable timeline of events to expect certain results.  

Although it is not uncommon to experience a notable odor in the first few weeks post rhinoplasty; (most often it is due to the dissolvable suture used to fixate the septum)... I would recommend you contact your surgeon for his opinion and evaluation as to the source. He would know what approach was used, and possible other extenuating circumstances involved with your procedure.