Jane,
As a dude who does this sort of thing for a living, I strongly urge you to contact your professional promptly and determine what you need to do. Since you cannot "unscramble the egg," you are faced with having title in your name and using your car partly for business. With all due respect to the helpful members on this forum, individuals who perform accounting and income tax services for a living and know the labyrinthine laws and regulations are much better qualified to give good advice and offer suggestions or alternatives to minimize your income tax burden while still complying with the law.
Your situation may not be as cut-and-dried as it seems. Your tax person can ask the right questions and propose what is best for you! Good luck!