Not that it's any consolation, but the same thing has happened to most everyone who uses helmets, and it's one of the 'live and learn' life events..
Depending on what cracked, and what brand of helmet you have, the manufacturer may offer replacement pieces. Arai, e.g., is very good providing replacement parts.
Depending on what cracked, and what brand of helmet you have, the manufacturer may offer replacement pieces. Arai, e.g., is very good providing replacement parts.