In an interview a while ago Jacob said that when he did the head banging scene in the Euphoria finale he got a concussion and was spitting blood when he got home.
He most likely just said it so people would respect him more, and he would get award show nominations, but it makes the show look very bad and unethical.
Sam (the creator) did an interview later and when asked about it said that it never happened and that he has no idea why Jacob would say that. Maybe he got over it, but he didn’t seem too happy about the situation in the interview.