“Is the Check Engine Light lit up? No
Or–even worse–is it flashing? Yes”
@TravisCampbell–A flashing CEL is an indication of engine misfire, and continuing to drive the car in that condition is going to lead to more extensive problems–if that has not already happened.
My advice is to park the car and use alternate means of transportation until you can read the stored trouble code(s)–of which there could be many on a used car with a (probably) unknown maintenance record–and do the required maintenance and/or repairs.
If you are lucky, you have “just” damaged the expensive catalytic converter by revving the engine and continuing to drive the car with a misfire condition, but other types of damage of a more expensive nature could have taken place already. For the sake of your wallet, don’t compound the problem by continuing to rev the engine or to drive the car.