How did I miss this??? I'm so sorry this sucks!!
I'd go out and check the hay ring, it could be something as simple as slag from a weld that can be easily filed/cut off. Run your hands around all the tubing. If it was from the ring, I'd make sure it couldn't happen again.
Not may people use it anymore but does that bale have baling wire used on it to hold it together? I came across one bale last year that had wire on it... Odd I know but worth thinking about.
I also would'nt rule out a kick. Top dogs get told off from time to time. Someone may have been challenging him and got in a shot.
Be strong and courageous, and do the work. Don't be afraid or discouraged by the size of the task, for the Lord God, my God, is with you. He will not fail you or forsake you.
1 Chronicles 28:20