Check Engine

My girl friend and her lady friends took my 2000 Volvo S70 out for the weekend. When they filled up, one of them forgot to screw the cap on the tank, and just kind of left it sitting on top. I didn’t know this till today when my check engine light came on and I checked the cap. Assuming that was the only problem, does anybody know if the light will go off on its own now that the cap is back on, or do I need to take it to the dealer?

The light shoudl go off on its own. It may take a few cycles.

Thank you.