Do I have a skin disease???

When I was 13, I noticed a kind of redish pink looking rash on my left foot, on the top. I am 23 now, and 10 years later a dime sized rash has grown to almost cover my entire foot.  The outside part of the rash is darker than the inside, and bumpy.  The inside of the rash has large bumps.  It just keeps getting bigger and is starting to grow up my ankle.  It doesn't hurt, nor itch, or anything.  But it's really starting to bother me, because these lumps keep getting bigger and the "rash" or whatever it is keeps spreading.  Anyone have ANY ideas?? You can't see it well in the picture, but it's darker ... more intense...
does ANYONE know??
thank u

Noctura