Do I have to pay for claim if clamiant didnt have repaired

My nephew hit a parked car with a go cart that he and his friends made there was damage to the bumper of the park car he opened a claim with his insurance company they paid him 976.00 on the claim he pulled the dent out with a plunger. My auto insurance of course denied the claim and his insurance company is seeking payment from me. Do I have to pay for cost labor and parts on a repair that was not done.