It should be something severe enough for Lucaon to whack him with his cain for every mistake and to start chaining him to the wall "again". It could be:
1. The VS solution; or
2. Something related to Ryan (because we can see that Lucaon doesnt like it when they're together)
Maybe he means it emotionally. We can tell when Kyon meets Lucaon he's pretty infatuated and he feels "caught" by his love for Lucaon. I have a theory that Kyon means to break the servant/master bond between him and Lucaon with the knife. So with the knife he's "freeing" himself.
Well..Kyon still owns the photos of young Lucaon... it could be related to that and maybe Lucaon finally put two and two together and found out that Kyon is the kid he saved while his parents were poisoned??? Maybe Lucaon still feels bad about not being at home on the right time..dunno what's going onf inis his head
I also had aa theory that what if the chaining part comes after Kyon cut off the collar..what of that was the punishment and that's why Lucaon hit him with his kane to make sure Kyon knows his place and who the master is..?
This is quite a considerable theory

What do you think Kyon got caught doing ? I mean that's how ch.1 starts, knife to his throat regretting getting caught. Theories anyone?