Can u grow a damaged marijuana seed that is slightly cracked

If just the testa (shell) is cracked, you probably can. If the radicle or plumule are disconnected from the cotyledon, maybe not, but there is still a good chance if they are close/touching.

Seeds are very resilient. They are designed to sustain harsh conditions such as falling from heights, being blown around in the wind, being stepped on, dehydration, etc.