How long does it take for nasal passages to clear up after a cold?

5-10 days on average. Could be few days sooner or few days longer. Depends on how bad the cold was, the anatomy of your nasal passages. Things to try to make it clear up faster: steam, neti pot (salt water flushes for the nose), decongestants, sometimes trying things like Flonase or Nasonex (mometasone) can also help.