Why does only one of my nostrils have mucus coming out of it at night time only?

Deviated septum: It would require and examination to be certain, however, a likely explanation is a deviated nasal septum, a common variation in the anatomy of the nose. You may consult an ENT doctor if the matter is concerning you. Wish you good health! - Have a diet rich in fresh vegetables, fruits, whole grains, milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Drink enough water daily, so that your urine is mostly colorless. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex, if you have sex.