Leak from bathroom sink behind the wall

hello , usually there will be water supply lines coming in from behind the wall area and if it isnt leaking at the supply valve it self then you may need to open up the wall area behind the sink and find out what is leaking it depends on what type of pipe is used most likely you have cooper tubing and sometimes these tubes after a while may leak or form small holes or it may be a leak at a soldered joint remeber there are 2 lines one for hot one for cold and you can turn the off by shuting off your water at the main valve then repair the leaking area.