A check engine light can be caused from something as simple as failing to tighten the gas cap after refueling so don't panic. If your engine goes into limp mode then that is more urgent. Stop at Auto Zone or any other parts house that offers a free OBD scan and you can get an idea of the urgency and then consult a repair shop if it appears to be urgent. Many times while towing there is a sensor that for whatever reason will send an incorrect voltage reading to the Engine control module or ECM, and later correct itself and the check engine light will go out and not return.