The only way he is going to fix that dent is by HIS OWN insurance meaning his rate will increase if he ever asked his insurance to fix it. I am sure his insurance won't even waste their time on this. Even if there involves court issue, the cop will be your witness. The cop will have to do that paperwork when either side request he to file it, but that does not mean it acts against you. The paperwork only shows what was at the scene. If the cop didnt think you caused the dent, there is nothing against you on that file.