Hi, Ammonia smell in the nose is often caused by Phantosmia, a brain related problem. The odor can range from pleasant to disgusting smells. Although the causes of phantosmia are debated, it is often comorbid with psychological disorders such as schizophrenia, mood disorders, Parkinsons disease, epilepsy, neuroblastoma, and frequent migraines. It is also caused by lack of enough carbohydrates in the body. You should consider increasing the percentage of carbohydrates in your diet and if the smell persists, go for a thorough check-up by a good Neurophysician. Treatments for phantosmia range from drug therapies (e.g., venlafaxine) and brain stimulation therapies to invasive surgical procedures involving removal of the olfactory bulbs or olfactory epithelium. Do consider a positive feedback as a credit to my work. Let me know if you have any further questions.