Check engine light came on right after I filled up the tank

A steady check engine light right after refueling is very often related to the evaporative emissions (EVAP) system, which checks that the fuel system is sealed. A fuel cap that was not tightened until it clicks, or debris on the filler seal, can trigger it.

First, check that the cap is tight and the seal looks clean. The light will not go off immediately even if that was the cause; the system has to run its self-test again over several drives.

A steady light with normal driving is usually not an emergency, but the only way to know is to read the stored code. Many parts stores and shops can scan it. If the light starts flashing, the engine runs rough, or you smell fuel, stop driving and have it checked right away, because a flashing light can mean a misfire that may damage the catalytic converter.