small pipe to kitchen sinks hot water has pin sized hole with water squirting out. I dont want to replace whole pipe for small hole. Will this work?

JB weld will fix this. Make sure the water is off for a while so the glue can set. It may be easier, however, to put a rubber clamp over the pinhole leak. You don't have to shut the water off. Just wrap the rubber around the pipe and screw the clamps tight.

It is a galvanized steel pipe. The squirting hole is close to the place where the nut is. Will it also seal the water from leaking around that nut?

I assume this is a galvanized steel pipe. This product may work temporarily if you use sand cloth and shine up the pipe all the way around and coat the epoxy all the way around the pipe. However the slag in the import pipe will continue to increase in size and you will ultimately have to replace the pipe. A better short term solution is a clamp type repair kit. It uses a clamp and a flexible piece of sealing " rubber type" seal. Regardless of the method remember this is a TEMPORARY fix and there may be significant damage from the next failure.