What action can I take if know that that I have been misrepresented by a lawyer?

It depends on the extent of the misrepresentation.  If it involved what is considered "legal malpractice" then you could potentially file a civil suit against the attorney for damages you suffered through the malpractice.   If you believe that the attorney broke any ethical obligation, you can also contact the Attorney Greivance Committee.  You can locate the applicable office here:  http://www.courts.state.ny.us/ip/attorneygrievance/complaints.shtml