In most people, the septum does not perfectly divide the nose into equal parts. A small deviation from the centre usually causes no symptoms unless the problem is at the nasal valve region. Problems arise only when the deviation blocks airflow through one or both nostrils.
This can happen if the front part of the septum becomes detached from the nasal floor and moves to one side narrowing that nostril. This can restrict or block airflow through the nostrils.
The nasal septum can also bend and take on an S shape. In this case, the tissue is misaligned and it can restrict or block airflow.