Delayed onset muscle soreness or strain: This is the most likely diagnosis given the history of an injury 2 days ago with initial pain settling, only to worsen later. The delay in onset of significant pain is consistent with muscle strain or overuse injuries that can become more painful as inflammation develops over time.

Contusion or bruising: If the injury involved a direct blow to the foot, a contusion could be causing the pain, especially if it has worsened over time as bleeding into the tissues causes increased pressure and pain.
Ligament sprain: A sprain, which is an injury to a ligament, could also cause pain across the foot, especially if the injury involved twisting or rolling of the ankle or foot.
Overuse injury (e.g., stress reaction or early stress fracture): If the individual recently increased their activity level or changed their exercise routine, an overuse injury could be the cause of the pain, especially if it's localized to a specific area like the metatarsals.

Compartment syndrome: Although less likely, compartment syndrome is a medical emergency that requires prompt diagnosis and treatment. It involves increased pressure within a muscle compartment, which can lead to muscle and nerve damage. Pain out of proportion to the injury, pallor, paresthesia, poikilothermia, and pulselessness are signs, though pulselessness is a late sign.
Deep vein thrombosis (DVT): While more commonly associated with the calf, a DVT could potentially cause foot pain if it involves the distal veins. This is more of a concern in individuals with risk factors for DVT, such as recent immobilization, cancer, or genetic predispositions.
Infection (e.g., cellulitis or abscess): If the skin was broken during the injury, there's a risk of infection, which could cause increasing pain, redness, swelling, and warmth over the affected area.

Gout or pseudogout: These are forms of arthritis that can cause sudden, severe pain in the foot, often without a clear history of injury. They are less likely in the context of a recent injury but should be considered, especially in individuals with a history of these conditions.
Osteonecrosis: This is a rare condition where the blood supply to a bone is interrupted, causing the bone tissue to die. It could potentially cause foot pain but is less common and usually associated with specific risk factors such as long-term steroid use or severe trauma.
Neuroma or nerve entrapment: Conditions like Morton's neuroma could cause foot pain, especially if the injury involved compression or irritation of a nerve. However, these conditions typically have a more gradual onset and specific locations of pain.