It is completely up to you whether you intend to claim or not. Your insurer will tell you that you must make them aware of any incident, this is not the case though. Under the Road Traffic Act 1930, the need to contact your insurer was because the insurer needs to be aware of anyone seeking rise to a claim. As you are not making a claim, then you do not need too. What I would say is that if the damage to his vehicle was that great, it is highly unlikely your vehicle is undamaged. I would get it checked out. You may well find that you need to make a claim and notify your insurer.