I agree with what others have said: the helmet needs to be replaced or serviced to have parts replaced.

A helmet is engineered to protect your head. It is not engineered to protect itself from a serious impact, and your impact was clearly serious. You can't necessarily tell if it's compromised just by looking at it: the critical parts aren't on the surface, inside or out. The helmet manufacturer probably has a web page with good info.

Also, any time you hit your head that hard a run by the hospital is a good idea ASAP. You may not notice a serious injury for as long as a couple of hours (see: Natasha Richardson). Ruptured spleens etc are also no good.