What can are my rights after trading my car?

I am 60 and had wanted a bigger and newer car. We knew a friend who bought and sold cars as a side job. He wanted to buy my old car. We traded cars as my boyfriend got a car in trade for painting a house. When we did this the guy was supposed to buy me a tire, battery and register my new car in lieu of payment. It’s been 5 weeks still nothing done on his end, but I made the mistake of giving him the old car. He wanted the key to my new car to put the battery in. Well, the result is he has one car and all the paperwork and the key and paperwork to my new car. He’s not doing his part. Is there anything police-wise I can do? He came to visit 2 days ago and left my old car in the street as it would not start. I went out tonight and took the plates off.