When you smell your own nostrils, the common causes are nasal foreign bodies with infection, sinusitis, sinus malignant tumors and so on. 1. Nasal foreign body with infection: when the nasal cavity is accidentally stuffed into the foreign body, especially the younger children, if not found in time, the foreign body is retained in the nasal cavity for a long time, it is likely to cause infection, nasal odor, and self-conscious nostril odor. 2. Sinusitis: for example, fungal sinusitis, fungal clumps in the sinuses, can also cause the symptom of foul-smelling nostrils, accompanied by pus flow, nasal congestion, headache and other symptoms. 3. Malignant tumor of sinus: if suffering from malignant tumor of sinus, i.e. sinus cancer, there will be prolonged pus and blood runny nose, unilateral nasal congestion and so on under the invasion of tumor. When the disease is in the advanced stage, some necrotic and dirty materials will be gathered in the nasal cavity due to the ulceration and breakage of the tumor, and a foul smell will be emitted. There are many other reasons why you smell your own nostrils stink, if the symptoms are difficult to improve for a long time, you must go to the hospital in time to find out the cause and timely treatment.