Check engine light

Your 1991 Camry is On Board Diagnostic level 1 (OBD1) it has pretty basic diagnostic capabilities limited to looking for opens and shorts in various sensors. Once the battery has not been disconnected the "fault" that caused the light to illuminate will be stored in the memory of the car's computer. You should get it checked for piece of mind. They may then fix the fault or choose to erase the code and see if it returns.