I am confused by your words:-
I need the sensor not being touched to go LOW
It is a sensor it does not go high or low.
Do you mean you want it to return LOW?
If so why, you simply do a logic inversion in your code, typically:-
sensor = !snesor
will do it, where sensor is a boolean type variable.
how do I turn off a pin?
Again not sure what you mean by that, but simply not reading it is a good start.