I recently rear-ended another car (right corner of my front bumper to left corner of his back bumper) at about 20km/h after he cut me off and immediately signaled for a turn. There was no damage to his car other than some scratches on the bumper corner. My car had a broken corner light, and also some scratches. Just today I was contacted by my insurance and told that he filed a "personal injury" lawsuit - absolutely ridiculous since the cars barely touched. What can/should I do?