How Can Marks On The Face Left By Pimples Be Treated?

My age is 31 years and weight 80 kgs. I had gastroenteritis during my teenage due to many pimples appeared on my face and back. Although the pimples have gone, they have left marks on my face. These marks are multiple round shaped penetrating into the skin. The penetration is not very deep. I want to know a suitable treatment for the same.