Found horse to have swelling inside right hind yesterday. No heat in the leg that I can detect, horse looks even on the lunge in both directions. (Just lunged him long enough to check for lameness.) To be on the safe side just walking him for a half an hour for the past two days.
Am I being paranoid? Getting from ribbing from a barn buddy about this ("If he's not lame, he's fine!"), but it seems better safe than sorry to me.
Is the swelling going down? If you palpate the area with his leg held up, is he sore anywhere? Any evidence of trauma (scrapes or scratches)?
If it doesn't resolve or markedly improve with a couple days of wrapping and cold and light exercise, I'd have the vet look if you are concerned. He *probably* just whacked himself with the opposite foot, but if you aren't confident in what you're looking at, it's better to be safe than sorry. Not all injuries (even major ones) result in lameness.
As Peter, Paul, and Mary say, a dragon lives forever.
Good news! The swelling has gone down by at least two thirds. I couldn't find any wounds when I checked the ankle yesterday, so I'm hoping that he did just knock himself. I'll keep an eye on that ankle for the next few days.