Once you hit your first nerve you will be seeking less nerve packed areas. Once was enough to turn me off of quads forever. That and the PIP that is.
First quad inject ever, pip was pretty bad. Since then, hardly noticeable. I love pinning quads. And as far as hitting nerves, I've done that a lot. It doesn't hurt, it's just a creepy feeling. Move the needle slightly and you're good to go.