there is a way to check it, someone in your local area prolly has a code reader, they are about 100 give or take 25. If not, I think autozone will read your code for free. Depending on what the code is, there are fixes available. Worst case senerio you can get a mil eliminater. If you are lucky the cel will go away after a few trips. If you had the car on, w/ the o2 sensors unplugged it can throw one.
Get the code read, and come back, someone will be able to help you.