Your leaving out the critical details!
First thing, check to see if power is going from the switch to the pump.
If no, replace the switch! These contacts sometimes arc and build up points that keep the other leg from making contact.
Above ground pump? if you have power at the pump but pump does not run, replace pump. If pump runs but does not pump water, it may have lost its prime. (possible a bad or leaky foot valve in the well.
One "tell tell" sign is that the pump gets hot quickly.
In-ground pump? It's possible you have lost the electrical connection to the pump. Many older wells were installed without spacers that keep the pump centered when it kicks on. Without spacers, the pump slams into the well casing, and in cases like mine, can smash or sever the wire.
My well is in my basement, I had to pull 70 feet of plastic pipe and the pump up and out through a small window into my driveway. I found the broken wires about a foot above the pump. Cheap fix, but pain in the butt job!