What Causes Brown Freckle On The Outer Ankle?

I've just noticed the sudden appearance of a small, black or very dark brown single freckle on my outer ankle. I'm 25 years old and used to tan in a tanning bed when I was younger, probably for about a total of 4 years or so. It doesn't itch or have any specific kind of feeling, and is not raised or textured. It's appeared within the last week or two. Is this something that can normally pop up or should I have it looked at by a dermatologist?