If he were mine, I'd gently tease his head out, if you have to peel the shell around the area that's fine. After that, he should be able to pop out of the shell on his own, but you can assist further if needed.
Could you take a few more, clear, up-close photos? The photo you provided is a little blurry.
Is the duckling yawing?
Do you see any active veins?
Everyone hatches their own way, and that's fine, but I personally never fully assist a duckling. I will take half of the shell, so their head and...