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. This may be your only recourse should your dog require expensive treatment. Others in your neighborhood may have reason to be grateful for written confirmation on a viscous dog. A 3-10 pound toy will not have the blood reserve of a larger dog and go into shock quickly. Cuts to the feet, mouth and head will often bleed profusely.