Blimey, that sure is some spint! My boy had two, one on each foreleg, which he had before i had him, and they've only just gone now, but luckily he was never lame with them! Hope your horse makes a speedy recovery!
is it hard yet-- or still soft-- if its soft its still forming-
you can get some clayice to , can put it on the outside and it will help cool and reduce splint aswell then wash off in morning
but its looking better than it did, splints are one of those things that take time to heal in there own right-- menaing can take a week can take 3 weeks or so depending on the splint --