Bathroom light switch issues

Hello! I am hoping someone out there can help me....
My bathroom light switch (pull cord) no longer switches the light off - just making it dimmer. It is constantly making a fizzing noise and there is a burning smell coming from it. Removing the bulb has not stopped the fizzing/ burning smell. Does this sound like a switch problem or a light fitting problem? We have switched the breaker off which has stopped the noise/ smell but is obviously not an ideal solution. One other thing - a month or so ago we had a water leak through the ceiling into this bathroom - could this be related (maybe getting into the switch somehow?).

Thank-you!

get an electrician to replace the switch ASAP

The sizzling is the interior of the switch arcing. This will continue to damage the switch, the wiring and possibly the ceiling . In the worse case you could have more than a kilowatt of heat being created in that switch without the breaker tripping and that is a serious fire risk.

DO IT NOW