The partition between the nasal cavities is called the nasal septum. It's made up of cartilage and bone. If the septum is crooked and causing obstruction, it is called a deviated septum.
A person who has a deviated nasal septum often has no symptoms or may have a crooked nose, problems breathing well through the nose (especially on one side), and a runny nose.
A deviated nasal septum may be caused by injury or surgery to the nose.
A person who has a deviated nasal septum that is not treated may have recurrent nosebleeds and recurrent nasal or sinus infections. If needed, treatment may include medicine to treat a runny nose or infection, or surgery to correct the deviation.