A brand left on Quark's forehead
Branding was the practice of burning an individual deliberately with the intention of shaming by leaving a permanent scar behind. If the wound was deep, permanent physical burn damage could occur. By the 24th century, dermal regeneration technology limited the severity of aesthetically altering wounds.
In 2370, members of The Circle branded Quark's forehead. After the attack, Doctor Julian Bashir assured him there would be no permanent scarring once he treated the wound. (DS9: "The Homecoming")