! This is a special case and makes sense since his trauma was that he never knew whether he was a clone or not and if he got hurt he'd disappear forever. He overcame this because he was forced to feel pain and found out that he still existed after the fact and given the circumstance of his crush being in danger this snapped him out of his fear over the matter. The underlying problem however, of the clones thinking they're real, might cause trouble in the future but only if a traumatic experience like before resurfaces. Until then, he's pretty much a free man and it made for a great character moment to show how powerful his quirk really is.
! And that's exactly how it doesn't work, which has been my gripe with the issue. It's a very common character arc in a lot of media: an event occurs, a troubled caracter is forced to do something he avoids or learns that he can do what he thought he couldn't do and then realizes that "everything was in his head" and it's perfectly fine. The past problem is then often played for laughs like in this chapter with the clones thinking all the other are clones except themselves. This is a subject that is widely missrepresented and not a particular issue with this manga (altough MHA does try to be more realistic about the themes it covers) and I don't want to derait the thread, so better leave it at that.