turn off check engine light on 2003 Volvo S60

How do I turn off the light. Light came on after my boy filled it up with gas and didn't get the gas cap tight

3 answers 2 comments
It may reset by itself eventually, but if you have a mechanic friend, see if he'll clear it for you for free with his scanner (maybe bring him a sandwich). I would for something like that for my esteemed customers.
The light will go off after a day or two if the loose gas cap was indeed the reason for turning it on.
But only if he keeps the fuel level correct to run EVAP leak test. It has to be between 20 and 80%.
Thanks for the clarification Zee.
You can try to disconnect the battery for a while and see if it will reset, if not, you need to take it to a repair shop to do it.

Zee