That is what a hoof looks like after the abscess has broken. You will not usually see drainage unless you are there right after it breaks. That little blister will just grow down the hoof. The coronet will return to normal and the hoof will not have a permanent scar like a cut on the coronet produces.
Your horse should stop limping on it. If he is still lame (at all) in another week, you should have the Vet out and have him x-ray it to see if there is something in there like a 'gravel' working its way up the hoof.