Give it a chance to cool down, I supposed by now that should have happened. Then drive it carefully home. I would try to avoid braking real hard. I've had this happen on my vehicles (more than one including my XJ), when they have sat a while.

You could take the cheap way out and pull the piston out of the caliper. Hone the cylinder and replace the seal and dust boot. Phenolic calipers tend to do this, in my experience especially if they are older. When phenolic calipers were originally used, somewhere in the late 70's early 80's, the phenolic would swell. They used to sell metal replacement pistons. Or you can just replace the caliper.