In a very tight road with vehicles parked on both side, I tried to pull in to allow a car to pass and misjudged the space and nudged the other car's bumper leaving a mark on my car and a mark on the other car as well. The mark on my car rubbed off and there appears to be no real damage, but I did see (I have dashcam footage) that the bumper on the other car was already scratched. I left a note under the car's windscreen wiper with my telephone number, took pictures of the damage and saved the dashcam footage. However, I have heard nothing from the owner of the other car. What should I do? Should I inform my insurance company? The police? I'm quite willing to admit it was my fault and would not like the to see anyone out of pocket because of my mistake, but the other car was already fairly scratched on other areas of the bodywork and I wouldn't like to be accused of additional damage. I'm also prepared to offer a contribution towards the repair of the original scratched bumper, if the owner wants to avoid going through insurance. What signed agreement should I get from them in this case?