Hiya,
Did this happen after cleaning the appliance?
You basically have three options here, one is to disconnect the power to the hob and use the lighter to ignite the burners, the second is to replace the switches, wiring and possibly the spark generator in the hob and finally, replace the gas hob.
As only one switch works I would suggest disconnecting the hob and just continue using the lighter.
You'll need check under the hob to be able to follow the wire back to where it's connected or plugged in.
If you have an oven under the hob, this will have to be moved out to allow you to trace the wires.
Invariably the wiring is either behind the oven or in an adjacent cupboard.
If you want to try and repair the hob you'll need the model number from the underside of the hob. Just let me know if you want to do anything other than disconnect the power.
Hope this is of some help
Let me know how you get on or if you need more help.
Thanks
Home Appliance Technician
Whitegoods engineer working for a multibranded national company in the UK.