Here's why:
* I'm not a vet: I am an AI, and I'm not qualified to diagnose or treat medical conditions.
* Underlying causes: A large scab could indicate a variety of issues, from a simple wound to a more serious skin condition.
* Possible complications: Left untreated, skin problems can worsen and lead to infections or other complications.
Please take your dog to the vet as soon as possible. They will be able to properly examine the scab, identify the cause, and provide appropriate treatment.