Purple swelling and pain in the middle finger may be caused by frostbite, trauma, septic dactylitis and other reasons. 1. Frostbite: Frostbite is a localized or systemic injury caused by low-temperature attack on the body, which is mostly seen in the hands, feet and ears, and when the frostbite on the hands is more serious, the purple swelling and pain of the middle finger may occur. 2. Trauma: If the fingers are hit by heavy objects or pinched by the door, it may lead to the rupture of local subcutaneous capillaries, bleeding, or poor blood flow caused by trauma, resulting in purple, swelling, pain and other symptoms of discomfort in the fingers. 3. Purulent dactylitis: Purulent dactylitis is a purulent infection of the subcutaneous tissue of the palm surface of the last joint of the finger, mostly due to finger trauma or inguinitis caused by a long time, the serious condition of the patient may cause purple swelling of the middle finger, pain, breakage of pus, local necrosis and so on. It is recommended that patients seek timely medical examination, treatment of the cause, in life, pay attention to monitoring the condition, regular review.