The wall between the nostrils that separates the two nasal cavities is called the nasal septum. It is made up of cartilage and bone and ideally should run down the center of the nose, equally separating the nasal passages. In many people, the septum is not straight, making one nasal passage smaller than the other. When the nasal septum is significantly off center, blocks one side of your nose, reduces airflow and makes breathing difficult, it is called a deviated septum. A deviated septum can also lead to sleep apnea, snoring, nasal congestion, sinus infections and nosebleeds.
Deviated septums may be congenital, meaning present at birth, or the result of an injury to the nose, such as a broken nose.