I fear the worst as his head appeared to be bobbling around indicating a serious neck injury
I wouldn’t call it a “kick” to the head. The Notre Dame player slowly placed his foot down under the USC player’s head, and then brushed the back of the helmet as he stepped past him. I’m not excusing the conduct; it was clearly intentional, and any deliberate contact with the head is out of bounds, especially after a possible head or neck injury. But it wasn’t a kick.
That would be a working link if you would not put any other HTML data in the post
http://thebiglead.com/2016/11/26/notre-dame-jerry-tillery-usc-video-kick-stomp/