Burn The Wound
In movies, healing a significant open wound typically merely requires burning and sealing it in some manner, such as with red-hot iron rods. Movie characters do it instinctively, as if it were clear that burning a bodily part that has already sustained injury is not only a good idea but would also instantly fix you and bring you back into the fight.
As surgeons still frequently use cauterization during complicated medical procedures, it is a legitimate technique to apply to wounds in order to temporarily close them up and prevent blood loss; however, it is not intended to be used as a first aid technique by the general public in the event of an emergency. Burning any wound simply puts a new wound on top of the existing one, causing the patient unnecessary additional suffering. More significantly, burn wounds are more likely than other types of wounds to become infected, which can worsen the situation if not treated right after.