The most common cause of a persistent blocked nose on one side would be that the nasal bone or septum is deviated internally to that side. The external nose may not look crooked. Usually, a very bad block results if the nose bone is crooked very near the entrance to the nose.
Sometimes, there may be polyps or tumors in the nose, so it is important that you see an ENT doctor if this does not resolve. A simple flexible nose scope in clinic will be able to exclude that quickly in less than 5 minutes, and will not be uncomfortable.
Another cause that is easily missed is a collapsed or weak nasal valve on that side of the nose. So when one breathes in, the soft lower part of the nose gets sucked in a little. As that is the area of an important nasal valve area, you may feel blocked on that side even if the nose bone is straight and there are no internal obstructions.
Kind regards,
Dr Lynne Lim
