Every helmet manufacturer warns that if the helmet has saved your melon, replace it. It is possible the helmet has damage that is not visible and could lead to serious injury in the next incident.
I have listed my helmet at the top of the list of insurance claims the couple of times a driver has put me down. When the insurance adjuster tells you that the helmet looks fine; look him/her in the eye and tell them that "You and I both know that every helmet manufacturer tells us to replace any helmet that has been in an accident." Neither adjuster gave me any further grief about the rest of my claim.