Post-Concussion Syndrome: This condition often occurs after a head injury, such as a hammer injury, and can cause symptoms like blurry vision, headaches, sensitivity to light, and sharp pains in the head. The fact that the injury was a month ago and the patient is still experiencing symptoms aligns with the timeline for post-concussion syndrome, which can persist for weeks to months after the initial injury.

Traumatic Brain Injury (TBI) Complications: Complications from a TBI, including subdural hematomas or epidural hematomas, could cause these symptoms, especially if the initial injury was severe enough to cause significant brain trauma.
Migraines: Triggered by the head injury, migraines could explain the sensitivity to light, sharp pain, and blurry vision. Migraines can be a direct result of trauma or could be exacerbated by the stress of the injury.
Optic Neuritis: Although less common, optic neuritis (inflammation of the optic nerve) could result from head trauma, leading to vision problems, including blurriness, and pain.

Subarachnoid Hemorrhage: Although the injury was a month ago, a delayed subarachnoid hemorrhage could still occur, especially if there was an aneurysm or vascular injury that has not yet been diagnosed. This condition is life-threatening and requires immediate medical attention.
Intracranial Hematoma: Similar to subarachnoid hemorrhage, an intracranial hematoma (such as a subdural or epidural hematoma) could be a delayed complication of the head injury, causing increased intracranial pressure and potentially life-threatening if not promptly treated.
Cavernous Sinus Thrombosis: A rare but potentially deadly condition that could arise from facial or head trauma, leading to thrombosis of the cavernous sinus and causing symptoms like headache, vision changes, and sensitivity to light.

Traumatic Optic Neuropathy: Direct trauma to the optic nerve could cause vision loss and pain, although this would be less likely to cause the full spectrum of symptoms described.
Pituitary Apoplexy: If the head injury affected the pituitary gland, it could lead to pituitary apoplexy, a condition characterized by sudden headache, vision changes (including blurriness), and potentially altered mental status. This is a rare complication of head trauma.
Cranial Nerve Injury: Specific cranial nerves (like the optic nerve or trigeminal nerve) could be injured during the trauma, leading to a variety of symptoms including pain, vision changes, and sensitivity to light, depending on which nerves are affected.