If possible, you need to put a bandage on the scab. You may want to put peroxide on it to make sure no dirt has gotten into it. I know a dog will chew at the bandage, but it won't heal if the dog keeps bitting at the scab.
How Do I Treat My Dog's Scab If She Broke It Open? She Got Cut By Wire And It Was Healing But She Pulled Of The Scab