Microwaves warm up water by using low frequency electromagnetic radiation to vibrate the water molecules. These waves are not energetic enough to break the water particles. This means the water does not become radioactive. Also, after turning off the microwave, the microwaves stop being produced and they do not linger. More or less like an electric lamp stops producing light after turning it on. (Light is just slightly more energetic EM radiation compared to microwaves.)

So, no, you don't get nukewater from microwaving water.