What you most likely have is a nasal polyp. These can occur spontaneously and tend to occur more in patients with sinusitis. I recommend that you see your doctor regarding this if you are having symptoms because of it such as runny nose, persistent stuffiness, decreased smell, pain, post nasal drip. You may require nasal corticosteroids to help treat it. In the meantime you can try nasal lavage with saline. This nasal saline spray can be bought over the counter.
If you have any questions, please feel free to ask. If no additional questions, please click accept.