Firstly, a broken leg, assuming the party being sued is legally at fault for causing your accident, would have a value in excess of the monetary jurisdiction in most states/localities. Secondly, if you properly filed a "notice of claim" with the correct municipality, and are being ignored, then the next step is to bring suit without further delay. Be aware, in most jurisdictions, there is a statutory time limit in which to file the "notice of claim", and also a set time limit in which to commence the lawsuit. With municipalities, those time periods tend to be shorter than if you were suing a private person or entity. You don't say how long ago your accident happened, so you better investigate this time issue, because if the time has passed you will be barred from bringing the suit. As a last point, if there is more than one party/person who might be liable for your accident, it might be dangerous to settle with one only, which is what it sounds like you did. It brings up issues of "set-offs" and/or deductions based upon what you got from the abutting property owner, which is too complex to tell you about on this site. You need to speak with a personal injury attorney in your area right away.
There is a very specific procedure for suing a municipality, which you have almost certainly NOT followed. See the controlling statute:
Contact the Worcester and MA bar associations for referrals, if you have not exceeded the notice period.
The foregoing is for general information purposes and does not establish an attorney-client relationship.