As @Philia_Bear mentioned it's not the service light, and can't be reset manually.
A fault code has been logged in the ecu.
I can almost guarantee youre engine oil is over filled.
You have a D5 model?
Oil level should be no more than halfway up the dipstick it's a common problem when people unfamiliar with Volvo's service these models. You need to drain the excess oil out and clear the fault code with a decent scanner.