How many days after a private car purchase do I have by law to return a car because the seller lied about the car and was not honest?

Last night I bpught a car from this guy and I spoke to him that same day on the phone and asked him everything about the car and also asked him if anything at all was wrong with the car which he said yes but just a few simple things to make it short he never mentioned that third gear was going out and grinding or that the car had a misfire so I went to buy it and test drove it I noticed that third gear grinded a bit but I thought it was me not shifting right, I still asked him about it which he said it was probably me getting use to the clutch which is a performance one, Well I also notice a misfire but I wasn't too worried about it and went on and bought it. While I was driving it home and shifting I noticed that third gear was grinding more and more so contacted him the next morning and he does not want to give me the money back. How can I get my money back? He lied.. this was in Tn