Cluster Headache: This diagnosis is the most likely due to the specific characteristics of the headache, including its location behind one eye, short duration (15 minutes to 2 hours), and associated symptoms such as tearing from the same eye and facial fullness. Cluster headaches are known for their severe, unilateral pain and are often accompanied by autonomic symptoms like lacrimation (tearing) and nasal congestion.

Migraine: Although migraines can present with unilateral pain and last longer than cluster headaches, some migraine variants, like ocular or retinal migraines, can have shorter durations and may involve tearing and facial discomfort. The key distinguishing feature would be the presence of an aura in migraines, which is not mentioned.
Trigeminal Neuralgia: This condition involves sudden, severe, shock-like pain around the eyes, lips, or nose mainly because of abnormal blood vessels pressing on the trigeminal nerve. While it doesn't typically cause tearing or facial fullness, the intense, unilateral pain could be confused with the symptoms described.

Temporal Arteritis (Giant Cell Arteritis): Although less common in a 22-year-old, this condition can cause severe headaches, often unilateral, and can lead to vision loss if not promptly treated. The presence of jaw claudication or visual disturbances would increase suspicion.
Acute Angle-Closure Glaucoma: This is an ophthalmologic emergency that presents with severe eye pain, blurred vision, headache, nausea, and vomiting, and can cause tearing and redness of the eye. The key distinguishing feature is the significant visual disturbance and elevated intraocular pressure.
Cavernous Sinus Thrombosis: A rare but potentially life-threatening condition that can cause headache, facial pain, and ophthalmoplegia (weakness or paralysis of the eye muscles). It often follows a facial infection.

Paratrigeminal Syndrome (Raeder's Syndrome): A rare condition characterized by a combination of trigeminal nerve dysfunction (leading to facial pain) and sympathetic nervous system dysfunction (leading to ptosis, miosis, and anhidrosis). It's a diagnosis of exclusion and would require further investigation.
Sphenoid Sinusitis: Although sinusitis can cause headaches, sphenoid sinusitis is rare and can present with deep, severe headache often described as behind the eyes, but it would typically be accompanied by other symptoms like fever, nasal discharge, or facial tenderness.