But when the septum is more than slightly off-center, this is the time when there is a deviated septum. It could be either a birth defect, or it could be the result of an accident or injury to the nose. In some cases, it is not a serious issue, but at times, it becomes so severe that it completely blocks the nasal cavity, and reduces the airflow. Most of the time, medications help, but if it is a severe condition, a surgery is necessary.