If you entered "nasal odor" into Google, you may have found yourself here. You are in luck. Here is what the people on this forum and a few of their medical providers have figured out so far. The odor, in most cases, seems to be caused by anaerobic bacteria thriving in your sinuses. The infection may or may not cause congestion. which is why your excellent doctor may not be able to detect it, so forgive him or her if they seem to indicate that you are crazy.
A neti pot or Neilmed Sinus Rinse probably won't be effective. That's because they are only effective in the lower sinuses--the maxillary and ethmoid--due to gravity. The nasal odor bacteria seem mostly to thrive in the upper sinuses, the frontal and sphenoid. Unfortunately, at this time, the most effective way to wash out the bacteria, which will cure the problem, is a Flip-Turn Sinus Flush. It is risky, because ideally it is done by bending over in a hot shower, but it can also be done outside on soft ground, in private of course.
It sometimes takes many treatments to get rid of the odor, and you should continue for at least 3 days after the stink goes away to keep it from growing back.
Finally, there are some medical conditions not caused by infection that causes people to smell phantom smells. I don't know much about those.
This discussion is related to Disturbing Nasal Odor