The light is coming from a diagonal from the top left corner...
Anyway, other than the muscles and some broke lighting issues I only have one concern. What is with the red "X"? When I see it I picture it as the perfect treasure seeking X that you find on a map, and it makes me want to go digging. ...Anyway aside from personal feelings about the red X if you intended it to be a scar you should make it more fleshy/scar-type because currently it just looks like a tattoo. Add depth to it on the far side of the if needed, and add a few color blemishes to symbolizes accent in the cut.