I bought a pre-owned car, a Hyundai i20 Active, 2018 model,at the dealership on the 3rd of April

I bought a pre-owned car, a Hyundai i20 Active, 2018 model,at the dealership on the 3rd of April. Within 21 days of the purchase I noticed that the car has signs of peeling off at the top and I informed them about it. I even took the car for them to check it. I was then told that they were not aware of such and they will get back to me. Currently the car is now peeling off at the tail gate. I took pictures and showed them. The salesman told me that he will show his manager and get back to me. He never did. Yes I understand that I bought a pre-owned car, but if I was aware that it was going to peel in this short space of time, I was not going to buy it. On top of that, the boot of the car is not opening.