D.B.
Almost all kids pick their nose. In my daycare the kids remind each other that it is unacceptable by saying "No picky and Flicky".
Many kids are not good nose blowers. Try to suction his nose with a good nasal suction device, and then put some vicks below his nose.
If his nose is itchy and dry inside he might just need some saline solution to make his nasal passages moist.
If he is doing it because there is nothing better to do with his finger, then make sure his hands are alway occupied with a small toy to hold.
He might just be eating it because there is no better place for it. Buy him his own hankies to collect them.
It he is eating them because he is hungry, make sure he always has a cracker in his hand.
The key here is to narrow down the reason he picks his nose and eats them.
I hope this helps
D.