Be aware of your dog's skull formation. Young pups can be awkward and are quite capable of walking into doors or skidding to a halt in direct contact with a table leg. Symptoms of a concussion are unmistakable. The dog may vomit, loose consciousness or sit with it's head hanging down. If the dog is conscious give 2 ml.
Light concussion is nothing to be too alarmed about.
However, unless you are very experienced, you can not make a judgment call between a light concussion and a severe knock which has caused swelling of the brain tissue. Generally a dog that proceeds to fitting, swelling of the forehead and odd vocalisation is a poor survival prospect. Your vet will need all of skills to pull him through. Large dogs tend to shake smaller ones by holding onto the scruff of the neck. Your toy may seem nothing more than slightly affronted when in actuality he may have sustained serious internal assault.