A hand abscess is a bacterial infection under the skin of the hand, usually caused by injury that introduces bacteria like Staphylococcus aureus. Signs of a hand abscess include a painful, swollen area of hardened or firm skin that is warm and red with visible pus buildup, and possibly a fever. The standard treatment is incision and drainage of the abscess by a doctor to remove pus and any foreign objects, along with antibiotics to treat the infection.