2012 Honda Civic - what do I do about a CEL?

check emissions light comes on. What do I do? Is it safe to drive?

This needs to be addressed.
First, make sure your gas cap is tight.
If light is still on:
You can have the codes read, usually for free, at an auto parts store such as Autozone then post the codes here. Format will be P0123, then we might be able to give you some ideas how to correct the problem.
Or, if your routine maintenance is performed at a mechanic or dealership have them check and correct the problem.