Hand and arm pain can be caused by an injury, repetitive motion as through typing or clicking a mouse, or overworking the muscles through exercise. Conditions such as gout or arthritis might also cause hand and arm pain, causing joints to become inflamed, swollen and very painful. An infection that occurs due to a laceration on the skin can also be painful, and will require treatment with antibiotics to be sure it does not spread throughout the body, which can be deadly. Identifying the cause of the pain as soon as possible will make it much easier to treat.
Some of the most common sources of hand and arm pain are through repetitive motion activities. Using a computer is a leading cause of carpal tunnel syndrome, which may even require surgery to fix in the wrist. Tennis elbow, or tendinitis, is another example of an injury caused by repetitive motion that is very painful. These injuries can sometimes be prevented by stretching and strengthening the hand and arm muscles; for example, pressing the hands together as if in a "prayer" position can help to stretch the tendons in the wrist. Generally, if the muscles are sore due to overworking them through regular exercise, an over the counter pain reliever can help to relieve hand and arm pain, while the muscles are allowed to rest for a few days in order to heal.
Actual injuries due to trauma may obviously cause hand and arm pain. A broken bone or a sprain can both be extremely painful, and will typically cause redness and swelling. If the break is severe, the hand or arm might actually look bent or deformed, especially in a compound fracture, in which the bone comes through the skin. Such injuries will typically require emergency medical treatment unless the sprain is very minor. It is best to keep the arm immobilized and put ice on it in order to keep the pain and swelling down as much as possible.
Lacerations, burns, or other superficial damage to the skin can also be very unpleasant. Generally these can be treated at home, unless the laceration is so deep or wide that it requires stitches. Cleansing the area with soap and water, and applying antibacterial cream and a bandage can help to prevent infection. Aloe vera gel applied to a mild burn can also help relieve the pain. Any laceration or burn with red streaks coming off it has become infected, and is spreading through the body, which will require prompt medical treatment.