I have a 2006 Hyundai Elantra that has error code P0111. on 2006 Hyundai Elantra

This occurred 2 days ago. I just changed the air filter today but it didn't look like it needed to be changed. The check engine light is still on. Auto Zone told me this could take a while to clear even if the problem is fixed.

Whats the next step(s) I should be doing? Is this a problem that could damage the car if I continue to run it?