Usually it is up to your former employer to decide if they want to try to enforce your non compete against you, and they may decide it is not worth the cost and effort to do so.
There are some situations, however, where it might make sense for you to consider initiating legal action yourself. One of these is if your former employer is actively interfering with either your new job or with your business contacts by falsely representing your obligations under a non compete agreement.
If your agreement is clearly unenforceable, and if your former employer is stating otherwise and causing you harm, you might have a claim for tortious interference with contract, and/or for unfair and deceptive business practices under Massachusetts unfair competition law. The viability of these claims will largely depend on whether your employer knows or should know that the agreement is unenforceable against you.