Was it screwed in or soldered?

Hopefully it was screwed in...otherwise you're going to have to demo a hole in the wall and have it repaired. If it's a screw-in pipe, wrap the threads with teflon tape, and screw it back into the fitting in the wall by hand; then attach the spout, again putting teflon tape on the pipe threads. When you screw the spout back on, both joints should tighten. If nothing was damaged, you applied the tape correctly, and you tightened everything properly, you should be good. If this seems beyond your DIY skills, call a plumber.