I had a CT scan which identified a nasal polyp on both sides and in the left frontal sinus. It's size is 22mm. How long can I wait with the surgery?

Can't examine you. Can't see your scan. Ask the professionals that know you best, your PCP or your ENT Specialist. Know that the longer you wait, the larger the neoplasm grows, the more it will erode surrounding tissues, the longer and harder the surgery and the post surgical recovery.
Depends. Although cancer needs be ruled out, it is a very rare occurrence. If you have no symptoms such as recurrent sinus infections, just repeat the ct in another 6 months to assess any progression in their sizes. If you do have repeated sinus infections, then they probably need be removed . Be sure that you don't have Aspirin exacerbated rhinitis.