By now, all the rough lines should have been rubbed out (sorry I did not mention it earlier...) Start to draw in the scales on the face and body. Crocodiles make good references for drawing scales.
I've drawn in rounded scales on the face and tapered scales on the body. Darken the edges on your line-art strategically to catch the shadows and light. Be sure to not fill your dragon's face completely with scales. Leave some white area for breathing space. Also, start to put in musculature on the face. A horse's face is good for reference for this dragon, since it kinda looks like a horse. If not, look at komodo dragons or monitor lizards.