What sad photos. :( Granted, horses are very tough creatures, but surely his reacted in some way to being hurt like that. I'm not going to fault Harry at all, but it looks like a deep wound, so I'm surprised he didn't notice his horse's reaction and realize the horse had been hurt.
it was an accident, might not even have been the spurs and could have been the stirrup, that's made out of metal too, should they ride horses without stirrups too?
Accident or not, the spurs need to go. I don't think stirrups could have caused that wound considering they don't have sharp edges. Metal in the stirrups, bit, etc., is just part of riding a horse, but spurs (even rounded) are unnecessary.