Pain under the big toe occurs for several reasons: First, toe osteitis of the toe: There are two toes at the base of the big toe and the bottom of the first metatarsal head. If there is inflammation of the toe bones or if there is a toe dislocation, this will manifest as pain under the big toe. Second, tenosynovitis: If the patient often walks with weight and sports activities, it may cause mutual friction between the lesser flexor tendon and the tendon sheath, which may lead to inflammation of the tendon sheath of the lesser flexor tendon, manifesting as pain below the head of the big toe, and when the tendon sheath is hyperplastic it may also be accompanied by popping of the toe and a feeling of not being stuck.