My Neff gas hob's igniter keeps firing constantly when the power is on?

Last night I had a major spill when a pan boiled over, it extinguished the main wok ring on my 5 ring ceramic Neff gas hob. I tried to re-light it a number of times whilst it was still rather wet and eventually the hob tripped the electrics on the circuit. I therefore unplugged the hob. This morning I checked the fuse and it's ok and so I switched the hob back on. Now the igniter fires constantly and all the rings light but when I touched a ring to adjust it, I had a very mild shock! It is now switched off and can only be lit with a match. Any ideas? Will I need to replace the piezo electric igniter and, if so how easy will it be to do and how much will it cost? I look forward to a solution. Thanks