What are the effects of lidocaine on a nerve?

It depends : The effects of the local anesthetics on nerve depend on the quantity and the location where the local anesthetic is relative to the nerve. Small quantities and close to the nerve can cause temporary numbness, however large quantities into the nerve itself it is thought to cause permanent damage. However, what quantity ; which nerve also have an impact on the quality of numbness or level of damage.

Na channel blocker: Yes, it is a sodium channel blocker, so it is used as local anesthetic and as anti arrythmic agent. Local anesthetics (lidocaine ) block the influx of sodium and prevent the generation of an action potential and its transmission along a nerve.