If I remember this was during the time after the incident with the fire, while en was still hospitalized and he met the inspector right? If so then I would guess that this was in connection with habaki finding out about en being a beta ( as we saw in later pages in the hospital) So when he met the inspector he had already seen the hospital documents and knew about en's true verse and about his struggles (en himself was still unconscious tho) and him touching his teeth was just him remembering the time he hurt his teeth and what had followed after that (also connected to the recent case with the beta who wanted to be an alpha... since he know knew that he had a beta who desperately tried to be an omega (for him) by his side).
I hope I could help.
Wait so did the seme actually bit that omega or not?? I’m still so confused on the first few chaps
Why did he touched his tooth in the last chapter? I remember that he broke it when he got crazy in school and thought he biten someone. For an insane moment I thought it was the criminal pretending and living as him lol