What Could A Dent Formation In Left Thigh Indicate?

I noticed a dent in my left thigh recently. It is about 4-5 long, 1-2 wide, and about 1/2-1 cm deep. I lost about 7lbs recently and have been under a fair amount of stress, but no other changes is my health and daily habits. I do not exercise and have never had or noticed anything like this anywhere on my body. There is no pain, tenderness, discoloration, obvious mass or anything out of the ordinary. I just a mysterious gap in my muscle that appeared very recently. I am 28yrs old, healthy,145lbs, 5 4 , 9-5 desk job, no kids. The only medication I take is Lutera for birth control. I also have PCOS, but do not see how that could have anything to do with that. Do you have any idea what the gap might be??