Car insurance claim

We’ve never been in a car accident before. Unfortunately my husband lightly bumped a car at some lights. They were green but he hadn’t braked hard enough (the other car was still stationary on the road). Luckily, it was a very minor bump. No dents or scratches, just a black scuff that we were able to rub off with our fingers on both cars. We exchanged details anyway, thinking it wasn’t needed. However, 2 days later the other car has made a claim against us. For what, we don’t know yet but we suspect it’s for money making. What is stopping them from going in for a service and putting all the problems they find on us? Do we have a leg to stand on? We’ve told our insurance exactly what happened, but we are not sure where that leaves us.

Edit: there is CCTV on the roadside, but we didn’t take any pictures. It was so minor we didn’t think it would come to anything but a wet sponge down on the black dirt on his bumper.