What sign would indicate that a patient may need emergency care after a head injury?

Vomiting after a head injury can be a significant indicator that a patient may need emergency care. This symptom may suggest increased intracranial pressure or potential brain injury, such as a concussion or more serious traumatic brain injury. The act of vomiting could be a response to the brain swelling or irritation caused by the injury, and it highlights the necessity for immediate medical evaluation.

In contrast, while headaches can occur after head injuries, they are relatively common and do not always indicate a severe condition. Feeling tired or fatigued can also be a normal response to trauma, but it does not specifically point to a critical problem that requires urgent intervention. Minor bruising, while an indicator of trauma, does not necessarily warrant emergency care unless it is accompanied by more serious symptoms. Thus, among the options provided, vomiting is the most concerning sign that requires prompt medical attention.