My old employer is releasing my medical information about a workers comp injury and I longer wish to allow him to do so. He has released me as an employee and is still telling customers I am on medical leave and giving our my info.

He's giving out your actual medical information OR he's saying you are on medical leave when you are not?

Depends what he's giving out.

You were fired by the company? You are no longer employed by this company?

... still telling customers I am on medical leave and giving our my info.

He is giving his customers information about your medical condition and treatment? What in the world would his customers want with that sort of information? And what makes you think he is doing so?