You might ask for a steroid pack. They just put me on one, and it helped immediately. The only problem is that as the dose tapers off over the week, the pain is coming back. But, it might give you more feeling for a while and help speed up the healing process.
If you study the facial nerve system you would be amazed at the amount of nerve fibers in this area. As you know, a dentist has to inject into this area to be able to cause the feeling of numbness in order to make a dental procedure far more bearable for the patient. Some nerves can get very "upset" if they are injected, but I don't know if you can actually call it "screwing up" on his part. If the nerve has only been bruised by the procedure it will heal itself. Unfortunately regeneration of the nerve may take weeks to months. Nerves are known to be very slow healers, but they do heal. You usually only encounter permanent numbness if a nerve has been completely severed. If your procedure wasn't oral surgery where scalpels were used to cut through tissue, then your nerve should gradually heal itself and little by little total feeling should be restored. As terribly frustrating as this is, time and patience is all that it needs. The fact that you can say it is getting better slowly is an indication that function is being restored to the area.
I'm having pain from the same kind of procedure. My dentist said that if you are allergic to novocaine, it can take the numbness longer to wear off--I don't know how long is longer. It could be nerve damage. Be glad you are numb and not in pain like me, if it's any consolation. It's not really a "screw up" from the doctor, because there is no way he can know for sure if he's going to hit a nerve--it's a calculated risk.