I just noticed this hard bump on my horses's back leg, he shows no signs of lameness even with a flex test. No heat, nothing. Maybe he has had it and I just failed to notice till now. Anyone else seen something like this? Ugh!!

Looks like he popped a hind splint. If you don't care about looks/blemishes, the bone is better now than before! 

 Oh good! So nothing to worry about, I can still compete on him?