Where/what situation has the O-Ring come from?
Have you pitched now?
In my very under edumacated experience about infections, and pretty much anything yeast knowledge based, opinion, I would be pitching ASAP!! Its worth the risk rather than writing off a batch over a little something like that - I have read tales of glasses falling in, phones, bugs and anything else you can think of and the beer ending up fine.....
From my understanding, the main case of infection is from wild yeast or an infection to the yeast in the early stages of its life... So unless that o-ring was coated in wild yeast or something that your brewing/pitching yeast eats and becomes a completely different strain instantly, I would be pitching ASAP and hoping for the best - what can you lose, the same as you are thinking of losing now plus a little bit of yeast!
So, time bomb? Maybe, maybe not - but a possible good beer is better than a tipped one.
2c + grain of salt.
BTW: Also, I would be beating that kid and screaming at it until he cries a heap!
:lol: - Obviously, just jokes!