I think I saw somewhere that it’s grows back but not instantly, it’s natural and slow.
Ok good
TW: Spoiler
I would've hoped for it to grow back natural and slow too but no. As to what I've read on the novel, the wing will indeed regrow but it is a painful process for the MC cuz the ML had to twist the roots(wingbone) back to its original form meaning ML had to dig his hands through MC's wound, then had the potion made by shiwoon's empire poured on it(this potion has the ability to regrow any lost limb, that includes wings). They had to do it cuz Sehyun HAVE to HAD the perfect symmetrical wings or else the vassals/retainers will despair and probly blame themselves for not being able to save him immediately and also cuz he's the image of the empire thing idk, this is done with Sehyun's consent and yes this sacrificial bastard insisted it.
Well damn, that sounds painful as hell.
If his qing grows back i might be a little mad since he went through all that pain just to have it grow back in a few seconds because of a potion but if it grows back normally then I won't be mad