what happen when you change a title on a car, because you lend the other person

[Mary]

money to buy the car and he ne? I loan my boyfriend 1,500.00 to buy a car with me holding the title until he paid me back, now he is say he isn't going to paid me back. so I change the title to my name, he is now saying that he is going to have me arrested if I don't give him the title. what can I do I don't want lose my money have a recored to