XD
He was jealous of his own fingers??
Since they touched her lips?? XDD
Its Cute but weird, but this is what it looked like
(Sry, i'm tired and it reminded me of some spoiler about "Villain's saviour")
Another theory, that is more likely thank the previous one:
he wanted to take advantage of the situation and kiss her, but he was too embarassed to do so.
Alright, g'night, i don't even clearly remembergh what i writedhb aboutbsndj
Maybe the joke they are refering to actually exists. But in case it doesn't: There's this old conception of the family in which the wife shouldn't be implicated in taking the actual high risk decisions. Ergo, good wives are the ones that don't rebel against their husbands and don't butt in their business. Keeping their own mouths shut. If they can sew it themselves, even better.
Is a mysoginistic joke extracted from it's original context inside a generally wholesome manga. If you ask me, that's genius.
There you go, now the pun doesn't make any sense because I explained it. At least there's hope the other joke exists, but we'll never now unless OP would clarify it. I'm sorry.