Suggest Treatment For Black Marks On The Face

I was not feeling good at work and they have a firstAid Kit,, and I was taking some of the med.and I got really swallon in my face,after that I had some black marks left on me by my mouth,,comes to find out the med,, was expired since 2012.what can I do to get rid of the black marks,?what can I get from the store to clear the marks??