Do we need a permit to do hardwood floors in Massachusetts?

The answer to your question is no.
There are several things that can be done in your home without requiring a permit in MA. One being flooring. Activities that may require a permit pursuant to other laws or bylaws a building permit is not required under 780 CMR R105.2 Work Eempt From Permit. Items such as fences not over six feet, retaining walls not over four feet, painting, papering, tiling, carpeting, cabinets, counter tops and similar finish work is exempt. There are several other instances as well but as for your floor, no you do not need the permit.
Hope that helps.