First and foremost is to clean your wound. Any dead skin should be cut away. Again depending on how badly you are damaged this might require an anesthetic and trip to the hospital. The wound will then have to be scrubbed with soap and rinsed with fresh water. This step should be repeated a few times.
To reduce the itching that comes with reef rash, you should then flush the wound with white vinegar or Isopropyl alcohol. Flush the wound or abrasion again with a mixture of 1/2 fresh water and 1/2 hydrogen peroxide. This will help remove coral dust and other contaminants that cause itching and stinging.
Apply an antibiotic ointment such as bacitracin to help prevent infection. You will have to rinse the wound with fresh water and reapply the ointment 3-4 times a day.
Symptoms of infection are continued itching, swelling, blistering, inflammation or ulcers. Red streaks moving up an extremity with blistering and pustular draining should be a sign that a visit to the doctor is necessary.
If after a few days your symptoms have not subsided it is suggested that you seek medical attention.