A nail nick can be cut with burrs in a rotary hand piece or using a drill press and the slide vise. It could be done with a burin ( engravers chisel), but that would be the hard way.
Engraving takes practice...lots of it. The tools and equipment can range from very expensive to moderately cheap. You can make simple gravers from O-1, W2, and 1095.
The real skill is in learning to cut the metal with control and not destroy the graver tip.