There have been many posts here similar to yours. Most of them involve visits to an ENT, Ear Nose and Throat specialist, or a neurologist. Some people believe it is caused by a bad sinus infection. Many have had their nasal passages checked, had various tests and MRIs done. Some have found relief with prescription sinus/ allergy medication.
If you would like to read over any of these posts you can type "smell smoke" in the gray search box in the upper right corner.