It looks like he had pipped through a vein. It's pretty incredible he's still alive. The way you went about assisting isn't really how it should be done. (Please don't take that the wrong way, it's easy to misinterpret things over the internet)
How you would usually do it, is open first just the air cell, like this. Sorry for the bad pic quality, but you get the idea.
View attachment 2290990
Put coconut oil on the inner membrane so it becomes transparent, and then watch and wait.
Once all of the veins have receded and there's no more yawning, chip away a bit more shell and ease the baby out.
View attachment 2290989How is your duckling now? Is he still yawning?