Don't worry.. Medicine available for good improvement......As the treatment varies depending on the severity... Send photos of the affected area, by direct online consultation for accurate diagnosis and treatment.

We will have to first examine whether the mark that you are talking about is just the pigmentation difference or there is also a difference in the texture of skin and then that modality of treatment would be decided accordingly.  You can consult with me by sending the pictures so that I can guide you on the right course of Management accordingly.