If a birthmark is broken and the skin is damaged, first, you should clean the area gently. Use mild soap and warm water to carefully wash around the broken part to prevent infection. Then, pat it dry with a clean and soft towel.
Apply an antibiotic ointment. The ointment can create a protective layer and prevent bacteria from entering the wound. Make sure to apply it thinly and evenly.
Cover the area with a sterile adhesive bandage. The bandage should be changed regularly, at least once a day or when it gets wet or dirty.
It's important to avoid picking at the scab that may form later. Let it heal naturally. If there are signs of infection such as redness, swelling, increasing pain, or discharge, it's advisable to seek medical advice promptly.