Always small end at the nock. And if you wrap it with sinew and thread, there is no problem with the nock.
Again, the voice of experience. I spent 4 nights in the hospital, 3 hours in surgery, and on anti-biotics for a month. A POC came apart on me on release and about 4"of the pieces went into my left index finger knuckle, where it blew up like a grenade when it hit bone. Thank goodness I had insurance, it was close to$500 grand before it was over with. The arrow cracked in front of the fletching and I didn't know it. In comparison to Tonkin. I shot a range and missed and buried my arrow in a Live Oak. I cut it out and shot 3 more targets before somebody pulled my arrow and told me it was split in front of the fletching for 4". It was still shooting with know change.
Bamboo will not come apart like that, even with nocks teensey- small, if you wrap them in front of the nocks.