A CEL means that the ECM has detected a fault in one or more systems, normally it is ok to drive it till you can get to the dealer , if your gas cap was loose the evap system would have picked that up on its normal system check and set the CEL the only way with OBDII to get it off is with a scan tool so off to the dealer you go should be covered under warranty in most cases !!!
Thsi is different the the maintanance required light which is for your OIL CHANGE REMINDER!