Umm i think it already healed you should check the rest of the page
But in the manhwa there's no mention that Rosaria has healing ability, right? as far as i know only guy named Drakun can heal himself
I think sensei forgot drawing the wound or something like that (●'◡'●)ﾉ
all of the Noblesse have a healing abilities, but there's exception for some Noblesse or Werewolf race they have a fast rate recovery and Edian only leave a scratch that's not realy fatal wound and Rozaria only began her battle recently. And there aren't any comments like this back at the official line webtoon website.
Uhmmmmm...excuse me Sensei!!! u miss the wound on Rosaria's chest from this page http://www.mangago.zone/read-manga/noblesse/mf/v07/c386/9/
(●'◡'●)ﾉ