I was rewatching the game highlights and on the OSU video that was just released at the end I heard one of the commentators say Howard could have run it in for a touchdown if he kept going. Why didn't he?

I remember thinking that while watching the game, but I was too excited about the win to give it a second thought...however, now that I've had a chance to rewatch it a couple times why wouldn't we want to score there? 

Or was that a business decision to prevent a potential injury?