The only herp vet I have been to in this state is Dr. Mertz at NE Wildlife in Weymouth. He's excellent. That would be a bit of a drive for you, but in a pinch, I would always recommend him!
If by North Central MA, you mean the Acton or Fitchburg area, then I don't know anybody out there. Hopefully another member from the area can chime in. You can't be too far from NERD - I wonder who they use for a vet?
Fitchburg area, yes. I know of a couple: Merrimack, Nashua, Westborough, and Chelmsford. I've heard that Nashua is way overpriced, though.