Any ideas why my engine light is showing on the dashboard of my 2003 honda accord?

First, make sure the gas cap is tight. Second, attach a scan tool or code reader to the Data Link Connector, located under the dash. Many AutoZone stores will do this for free. Your Check Engine Light came on, because a code was thrown and stored in the ECM. If it was caused by a loose gas cap, it will go out on its own. Otherwise, you will need to repair what is wrong and reset you computer.