Put an air filter over your carb and don't sweat it. What you should do is turn over the engine any time you have ground contact. The only real damage that you might do to the engine is bend the crankshaft which is unlikely. The engine mount could break too, but again, on a nose over it's unlikely.

If the crankshaft is bent, you'll be able to tell when you turn the prop over.

BUT! Always check your prop carefully for small cracks. If a blade flies off, somebody could get hurt or it could fly through someone's plane. If then engine isn't shut down immediately, a lot of damage could occur from the unbalanced load - broken engine mounts, broken firewall, etc.

not trying to scare you because as has been said, the most probable damage is a broken prop, but you should check over the plane for safety.