Hello, A musty smell in the nose is indictive of a sinus infection. This can be acute or chronic. Get clinically examined by an ENT, get X-ray PNS done. Take mucolytics containing bromhexine to help clear the accumulated mucus. Decongestants are effective. Steam inhalation at least once a day on a regular basis will be very helpful to clear it. Taking antihistamine at bed time will give relief. Sometimes reflux from your esophagus can cause a nasty taste in the back of your throat which can affect your sense of smell. Take antacids or PPIs to get rid of acid reflux and hence the symptoms. People suffering from liver disease, including cirrhosis, also complain of a characteristically musty smell in their breath. Dimethyl sulfide is chiefly responsible for the musty smell. Get liver function tests done to stay on the safer side. You will be accordingly treated. Reduce or eliminate alcohol use. Reduce the consumption of rich foods like red meat, trans fats, and processed carbohydrates. Exercise regularly. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K., General & Family Physician