Looks like Pigeon Fever to me, too. It is in the right place. I would also expect the swelling below the first one to break open, too.
Call your Vet and ask if it going around your area. It usually is seen during or after an extended drought or hot, dry weather. We have had a 2 year drought in 2011 and 2012 and there was more Pigeon Fever around than anyone can ever remember seeing. We had 2 cases last year -- two different horses in two completely different herds that never got near each other. It just pops up with cases here and there and all unrelated.