What happens if a dog’s head is injured?

A head injury may cause crying, flinching, and not wanting the head touched from pain. Nerve damage brings dizziness, wobbling, circling, eye tremor, uneven pupils, vision or hearing loss, facial palsy, drooling, seizures, coma.

Severe injury can cause intracranial bleeding and concussion with headache, nausea, vomiting, confusion, drowsiness, dilated pupils; see a vet if these appear.