Swollen flesh next to the nail on the left thumb may be caused by soft tissue injury, gingivitis and other diseases. 1. Soft tissue injury: the left thumb by external forces or excessive activities, resulting in local soft tissue damage, will cause the symptoms of swollen flesh next to the nail, accompanied by varying degrees of pain. You can apply ice packs within 24 hours after the injury to shrink the capillaries and prevent swelling, and you can be treated with ibuprofen, diclofenac sodium extended-release tablets and other drugs for pain relief. 2. Nail groove inflammation: the left thumb nail repeatedly inserted into the flesh or trimmed too short, will lead to local skin ulceration, causing infection, the phenomenon of left foot thumb nail next to the flesh swollen. You can take cefradine, levofloxacin and other drugs for anti-infection treatment. If an abscess is formed, it can be treated by abscess incision and drainage. Therefore, the left foot thumb nail next to the flesh is swollen patients, should go to the hospital as soon as possible to check, clear the cause of the disease and actively cooperate with the doctor for treatment.