There are many reasons for sudden thumb pain, such as trauma, arthritis, infection, degenerative changes, osteophytes and so on. 1. Trauma: If there is a clear history of trauma to the thumb, it can cause local soft tissue contusion, skin rupture, etc., and in severe cases, it can cause tendon strains, and thus pain occurs. 2. Arthritis: Inflammation of the joints of the thumb can also cause pain, such as rheumatoid arthritis, osteoarthritis, rheumatoid arthritis and so on. 3. Infection: For example, onychomycosis, which is mostly caused by pulling out barbs, nail embedding and other factors. Secondly, the presence of inflammation of the thumb follicle, skin soft tissue infection can also cause pain. 4. Degenerative changes: middle-aged and old people may experience degenerative changes in the thumb joint due to ageing, which may also cause pain. 5. Osteomalacia: Osteomalacia of the thumb due to age-related factors can also cause pain in different degrees. There are many reasons for sudden pain in the thumb, it is recommended to go to the hospital in time to improve the examination and give standardized treatment after a clear diagnosis.