I think this song can be interpreted in different ways, one being that after this relationship he was "addicted to" or using as a coping skill ended and he turned to other coping skills, like self harm. He could have turned to drugs, abuse, anything, and it harmed him and he needed professional help, like a doctor who gives stitches, to stop or at least recover. The other way it could be interpreted is he has a shattered heart and needs stitches to put it back together, still implying that he needs help. Whatever it means, its says that whatever relationship he had, he needed help to heal after it ended. Maybe it was kisses from a lady and now its kisses from a razor blade to cut, kisses from the motherland of drugs, the painful kiss of abuse or fighting, to get over the relationship.