My dog has a black spot on her back, is this normal?

My 3 yr old female Schnoodle (schnauzer/poodle mix) got a quarter sized black spot on her hind quarters under the hair about a month ago. It bumped up a little, then started to flake. It didn't seem to bother her, even when I touched it. It's now back to normal, but the skin in that area is still black & the hair growing from it is darker colored & more coarse. Is this a normal occurrence? Thanks in advance.