1) Do not stop, do not pass go, just go directly to a doctor. It could just be irritated from you scratching at it, or you could be developing a very protracted infection - either way, it's best to get it looked at ASAP.
2) Itchiness *can* be a sign of nerves re-connecting, especially if the area has been numb/ had reduced sensation since surgery.
3) Don't scratch healing wounds. Ever. Seriously. If you *must* do something, place a cool cloth over the affect area and scratch an area above it - it will trick your brain into thinking that you scratched where it itches but you actually haven't.