My neighbor who lives directly across the street from me, often parks his car or truck in front of or behind our already parked vehicle(s) in front of my home. The space is just enough room for one large and one compact size vehicle. He always either pulls up too close practically lifting the rear end of our vehicle hitting our bumper or backs into our vehicle. I've seen our vehicle(s) bounce forwards when he makes contact. He never then moves back he just leaves his vehicle as is with not so much as an "I'm sorry". I have seen him do this from my window. Although I have asked him in the past not to park too close to our cars, I don't always say anything because he has been a long time neighbor. How bad do damages have to be before I can call police?
You can always call the police to come to the scene and make an accident report. This may deter him from future incidents. He could be cited for failure to keep a proper lookout and failure to control speed (amongst others). Also, if he is constantly hitting your car, he may be doing it intentionally or he may be under the influence of alcohol or drugs.
In short, you do not need major damages to call the police and you should report this the next time it happens and tell the officer of the previous incidents. It can't hurt to make the report, and may deter him from hitting your car. Also, many other things besides a citation may happen. For example, he may not have proof of insurance, inspection, registration, or a valid driver's license; may be under the influence of alcohol or drugs; and may even have outstanding warrants. This may result in multiple citations or even his arrest.