Also is it both or just one nostril that is bleeding. If it's both then normally that means the blood is coming from the lungs, which is life threatening.
If it's just one normally it is ok he may just bleed but I would DEFINITELY get the vet out to check it. If it's the work he's doing, then you can try to adapt and fix it, if it's his food then you can change it, and if it's something else then your vet will give you the best options
Get him scoped. It could be a very serious condition. If it happens at rest, it could actually be life threatening. If it happens after work, he is a bleeder, and there are supplements for that. Either way, have a vet check him.