Hypopigmentation after a burn is usually due to the destruction of the melanocytes. Treatment for this condition is not easy as there is a lack of melanocytes to restore the pigmentation. As my colleague has pointed out uses of various devices may improve the pigmentation with a combination of a particular type of filler injection called Rejuran - which contains Salmon DNA and possibly can help aid in repair.
Alternative a more invasive and cheaper way would be to have the scar excised under local anesthetic. This would result in a small linear scar and over time would return to your natural surrounding skin pigmentation.
If you would like to know more please don't hesitate to contact me.