Reddish / Purple Rash On My Inner Thighs, No Itching, Cortisone Cream, Skin Feels Tender, Hispanic With A Golden Brown Skin Color

For ten months, I had a reddish / purple rash (no itching) on my inner thighs. I used a cortisone cream, but stopped using it since there was no change. A month ago, I noticed that my upper inner thighs are a dark purple-black in color. The skin feels tender especially if it wrinkles . I am Hispanic with a golden brown skin color and have never encountered this problem in the past. Should I be concerned? RC