How do you get rid of the numbness from a novocain (procaine) shot so you can function?

Tincture of time. Although there is an injectable drug that can reverse the effects of local anesthetic (phentolamine mesylate), patients tend to resist the idea of additional injections. The most practical approach to abolishing numbness is to allow time for nature to take its course. In the future, you might consider asking for an anesthetic without a vasoconstrictor, as this has a shorter duration of action.
Takes time. It would help to know what part of your body the injection affected, but basically there's nothing you can do but wait. The numbing medication will wear off in time, usually no more than a couple of hours. There is no antidote or way to reverse the numbness. Be careful to protect the affected part of your body in order to avoid hurting yourself accidentally while it is still numb.