confused why he threw up after the kiss tho what

I went back and looked at that whole weird scene in ch 13, and the thing that struck me is that that ”black stuff” that Guowon has tattoeed on him is in that scene all the way up and over the ”stitches” on his neck…where normally he has his neck just skin-toned. Afterwards, when he looks in the mirror again, it’s back to how it was before.

So…a mistake by the artist or a plot thing?
Is the scene about chock or trauma, or is it because the kissing made his condition worse for a while?