I have seen the really big deal too. This one did not look like that though.. His nose (all down the front of his face) swelled up. He had cracked, retained teeth that got impacted and infected with a huge mess of grain. The first clue was his breath smelled like POO (poop)..
I mean very bad and so obviouse. Then the face swelled up.. What a mess. The first vet charged several hundred dollars after -rays.. He was lazy and took another vet to take care of it..
Poor horse was only two.. I can go into detail sometime if anyone wants to know. The face swelling never went away. MAJOR anitibiotics had to be given and feed change done.. This does not look like your horse does.. Smell his breath. If is smells like Poo (poop) do not delay..