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?

edit: Also, be careful with unrecommended "herp" vets. I got ripped off by taking my snake to a supposed reptile vet who knew less than I did about herps. They will charge you an arm and a leg for a useless visit. Try asking around on Craigslist or with any local herpers that you may know.