If it is on both sides of the nail, it is caused by nail fungus; if it is in other parts of the thumb, it may be caused by a foreign object that has been inserted into the thumb and caused by pus after infection. If it is a nail infection, you need to cut both sides of the nail to drain the pus and check the depth of the wound. If the wound is shallow, you can change the medication on the wound; if the wound is deeper, below the remaining nail, you need to remove the nail and continue changing the medication on the wound at a later stage. If the abscess is caused elsewhere in the thumb, the surface of the abscess should be disinfected and then cut open to drain the abscess, and a vascular clamp should be used to detect any foreign body inside. If there is a foreign body, the foreign body should be removed and the wound should be changed and treated with oral antibiotics at a later stage.