I get the same thing in my ankles and my hips..The popping sound.
And I run 7-10 miles for a good workout with no trouble, and just graduated a belt testing with a flawless break of two boards, by means of a side-kick (mechanical knee-in-kne-out movement) in my taekwondo club....All with little to no pain.

UNless this is really hurting you, it's nothing to worry about.
Sometimes joints and cartilage just make funny sounds when they're shifting around. ^_^