If it is a serious bite, call 999.
Clean the wound immediately by putting tap water over it for a few minutes.
Remove anything from the bite like teeth, dirt or hair.
Try and make the cut bleed a tiny bit unless it is already heavily bleeding.
If the wound is bleeding heavily, put a clean pad or dressing on it.
Dry the wound and put a plaster on it.
Take painkillers or calpol if the wound if still hurting.