Migraine: A common condition characterized by recurrent episodes of severe headaches, often accompanied by sensitivity to light, sound, and nausea. The pain can be unilateral and may radiate to the head, making it a likely diagnosis for nerve pain going into the head.

Tension Headache: Frequent or chronic headaches caused by muscle tension, often described as a band or a squeezing sensation around the forehead, back of the neck, or both. This could be mistaken for nerve pain.
Occipital Neuralgia: A condition characterized by inflammation or irritation of the occipital nerves, which can cause severe pain in the back and top of the head. The pain can be sharp and stabbing, similar to nerve pain.
Trigeminal Neuralgia: A chronic pain condition that affects the trigeminal nerve, which carries sensation from your face to your brain. It can cause intense, shock-like or stabbing pain in parts of your face, including the head.

Subarachnoid Hemorrhage: A life-threatening condition caused by bleeding into the space surrounding the brain, which can present with sudden, severe headache (often described as "the worst headache" ever experienced). Although less common, it is critical to rule out due to its high mortality rate.
Temporal Arteritis (Giant Cell Arteritis): An inflammation of the blood vessels in the head, which can cause severe headaches, jaw pain, and vision problems. It's essential to diagnose promptly to prevent complications like blindness.
Meningitis: An infection of the protective membranes covering the brain and spinal cord, known as the meninges. This condition can cause severe headache, fever, and stiff neck, and requires immediate medical attention.

Cluster Headache: A rare but extremely painful headache disorder, characterized by recurring cycles of headache attacks. The pain is typically one-sided and centered around the eye.
Hemicrania Continua: A rare headache disorder characterized by a continuous, one-sided headache of moderate intensity, with episodes of more severe pain. It's often accompanied by autonomic symptoms like nasal congestion or eye watering.
Cervicogenic Headache: A rare type of headache caused by referred pain from the cervical spine, often due to injury or inflammation of the cervical joints or muscles. The pain typically starts in the neck and radiates to the head.