Pain in the lateral aspect of the thumb is usually due to inflammation, trauma, and other causes. If the pain is mild, reduce thumb activity and observe the pain relief. If the pain is severe, it is recommended to visit a hospital promptly to identify the cause and treat it under the guidance of a doctor.1. Inflammation: Pain in the lateral thumb may be caused by local inflammation due to strain, such as stenosing tenosynovitis, often due to strain on the thumb caused by repeatedly performing various grasping and holding movements of the thumb. The pain is especially aggravated when the thumb is lifted, and the pain is located at the stop of the greater interphalangeal muscle of the hand. If the pain is on the lateral side of the nail of the thumb, it is commonly associated with inflammation of the nail and lateral nail wall of the thumb, while often accompanied by typical clinical manifestations such as redness, swelling, heat and pain, which may lead to septicemia in severe cases; 2. Trauma: pain on the lateral side of the thumb, which may also be related to trauma, including contusion, breaking and impact injury, can lead to injury to the lateral collateral ligament and joint capsule on the metacarpophalangeal joint side of the thumb, and local pressure pain will The pain will be aggravated by local pressure. You need to pay attention to the protection of the thumb on a daily basis by not overusing the thumb, tearing barbs, trimming the nail too deeply, or causing trauma to the thumb. If the pain on the outside of the thumb is severe, it can be treated with blood-activating, anti-swelling and pain-relieving medications under the guidance of a doctor.