You can wash it off with toothbrush, alcohol, washing powder and water. The specific steps are as follows:
First, take a proper amount of laundry detergent to cover the place stained with black ink.
Second, soak in water for a few minutes before rubbing.
Third, smear the place stained with black ink with alcohol.
Fourth, gently brush the place stained with black ink with a toothbrush.
5. Finally, rinse with clear water and dry.