Broken helmet and transient discomfort... earned me £300 when a Skoda driver (and coincidentally a friend of my ex wife!) Scooped me off a few years ago. Side of my neck was sore, but was fine the next day and I wasn't going to lie about it - 6 or 8 months in Chokey ain't worth a thousand pounds or so.
If its a visible mark, or pain that lasts beyond the day of the incident then it would be considered an injury and he'd be potentially in line for more.
I must point out as plod myself that over 24 years member of the public have written off 4 police cars I'd been driving, but I don't waste time flapping my gums over it. A chump is a chum is a chump, and being a milkman, policeman, arms dealer or nun won't change it.