Hi, any infection or blockage in your nose can cause you to smell something that is not there. Your symptoms could be due to olfactory hallucinations. Phantosmia most often occurs as a result of a head injury or upper respiratory infection. It can also be caused by temporal lobe seizures, sinusitis, brain tumors, migraine, Parkinson's disease and stroke. You may need proper evaluation by your GP, please consult him for a neurological assessment. He may then refer you to a neurologist if needed. Regards.