What Is The Treatment For A Dark Patch In The Leg?

Hi. Last year I had a small lump on an old scar on my left leg that was very itchy. It later turned into a scab. My GP prescribed an ointment for eczema. It took a long time to go and has left a large dark patch on my leg. I now have one on my right leg. again it came up as an itchy lump which has now turned into a scap in a round shape with little clusters of darker scabs on it.