My Daughter Who Is 4.6 Years Old Hurt Her Forehead

My daughter who is 4.6 years old hurt her forehead against the sharp edge of the center table. It left a small cut on her forehead. We took her to the nearby doctor in our locality. She was prescribed silverix ointment to be applied 2 times a day.

It's been 3 days ever since she got hurt. Since yesterday, we could see a black spot on the forehead of my daughter where silverix is being applied.

what could be the reason for this block spot on my daughter's forehead?

Please advice.