Sorry to hear about the flight!

It was a good thing the engine was at idle!
Had the carb been opened, dirt and related will have gotten into the engine, and caused major damage internally.
It is a good idea to check that firewall as stated above, and repair the crack. If you fix this, and don't want to wait for an order of covering,
use clear (not the translucent type) scotch tape to hold the covering for the time being - If it works on my Cub, it'll work for you!

Join the nearest club, and get an instructor to check your model after the repairs - he might spot something you hadn't.

Happy flying!