Digital Nerve Injury: This is the most likely diagnosis given the history of injury and the symptom of numbness in the fingertip. The digital nerves are responsible for sensation in the fingertips, and an injury can cause damage to these nerves, leading to numbness.

Fingertip Laceration with Nerve Damage: A laceration to the fingertip can damage the small nerves that provide sensation, leading to numbness.
Finger Fracture with Nerve Compression: A fracture in one of the finger bones can compress or damage the digital nerves, causing numbness in the fingertip.
Soft Tissue Injury (e.g., Crush Injury): A crush injury or other soft tissue damage to the finger can also affect the nerves and cause numbness.

Compartment Syndrome: Although less common, compartment syndrome is a serious condition that can occur after an injury. It involves increased pressure within the compartments of the finger, which can compromise blood flow and nerve function, leading to numbness, pain, and potentially permanent damage if not promptly treated.
Infection (e.g., Abscess, Cellulitis): Infections can cause numbness and tingling if they involve or compress nerves. Early recognition and treatment are crucial to prevent serious complications.

Raynaud’s Phenomenon: This condition causes some areas of your body — such as your fingers and toes — to feel numb and cold in response to cold temperatures or stress. While it's less directly related to injury, it could be considered in the differential if other causes are ruled out.
Neuroma: A neuroma is a growth or tumor of nerve tissue that can develop after a nerve injury. It's less common but could cause numbness or tingling in the affected area.
Vascular Injury: Direct injury to the blood vessels supplying the finger could lead to ischemia and numbness, although this would typically be accompanied by other symptoms such as pallor, poikilothermia, and decreased pulses.