The best way is to replace the switch. First, turn the electricity off to that switch. Remove the cover and the screw holding the switch in place. Take the wires off the switch. Replace in the reverse order.
Turn off electricity by switching off circuit breaker. Disassemble switch and check if the wires are still connected to terminals. If a wire has been burnt and disconnected - clean it and reconnect. If wires are intact - turn electricity on and check input voltage. If it's available toggle switch and check output voltage. If it's zero - replace switch.
First make sure you have power there. Secondly, make sure you have the switch let going up to the light. You may also want to check for a loose neutral. It could be many different things that are wrong. The switch may be bad.