I flipped the picture and made it smaller so we could all see it. Heres what i can see:
The head looks a bit big compared to his body, at the very least his neck should be a bit thicker
His eye should be moved up or the 'eye ridge' should come down farther so that the eye is actually in it
From this angle you should be able to see part of a second horn, if he has one, and his other wing
His legs should be longer and his shoulder should be higher up on his body, I would suggest looking at a horses body for a reference
His legs and wings could stand to be a bit larger, there really isn't a chance that this dragon could fly with wings that size
Overall its a very good start, especially if this is one of your first dragons. It takes some practice and patience and I'd suggest checking out some anatomy of 'similar' animals. Horses Dinosaurs lizards cats birds and bats, dragons take body parts from real animals so study some of those to get a better feel for what they should look like
Hope that helps, and sorry if it seems like a lot of critique at once.