When you're affected by a poison you make your save against the affect every round on the turn you were afflicted.
If you were afflicted by an AoO on your turn that is when the recurrence affect would happen. When on your turn though would it happen? If I'm a pally with the remove poison lay on hands can I activate that to not be affected by the poison on the recurrence next round? Or would i take the poison damage and then have to do the lay on hands? This is assuming I forgot that I could cure the poison on the initial round of attack.
The CRB example for poison stacking says "rolls his save on the next 8 rounds"
But it also says that injury poisons often has no onset time(it works immediately).
The way I would rule: you save immediately when hit with a poisonous attack when it's your turn.
So you would have to save at least once before you gat a chance neutralize poison.(unless you can do so as an immediate action - because that would be cool...)