There’s no warning-sign list just for the arm. The elbow is one of the bony spots where pressure sores form, but the rest of the arm is not, and leg ulcer advice doesn’t apply here at all. So for most arm wounds, the general signs are the ones that count.
Contact your provider right away for redness, increased pain, or yellow or green pus, or excessive clear fluid around the injury. These are signs of infection. Also contact your provider right away for black edges around the injury, which is a sign of dead tissue; bleeding that will not stop after 10 minutes of direct pressure; fever of 100°F (37.7°C) or higher for more than 4 hours; pain that will not go away even after taking pain medicine; and a wound that has come open or stitches or staples that have come out too soon.
The more useful thing for an ordinary arm wound is knowing what the first few days are supposed to look like, because that is what gets mistaken for infection. Once the scab forms, the wound becomes slightly swollen, red or pink, and tender. Some clear fluid oozes from the wound. This fluid helps clean the area. This stage takes about 2 to 5 days.
Put that next to the infection list and it falls into place. Clear fluid is expected; it is *excessive* clear fluid that is on the list. Pink or red skin is expected; it is redness with *increased* pain, or yellow or green pus, that is on the list. Tenderness is expected; pain that keeps rising, or will not go away after pain medicine, is not.
What should happen next is also clear. The wound starts to fill in with new tissue, called granulation tissue. New skin begins to form over this tissue. As the wound heals, the edges pull inward and the wound gets smaller, over the next 3 weeks or so. An arm wound going the other way — more swollen, more painful, more fluid, on day six than on day three — is the pattern worth reporting.