The payment to silence Daniels just before the election appears to be an illegal campaign expenditure, regardless of who paid for it. If Trump knew he was part of violating campaign law, that would be criminal. Previously he had tried to claim he didn't know what Cohen was doing, which might have been cover. But here he said that he knew Cohen was representing him in the "deal" as he put it, so he's back on the hook for that.
Also, he has lawyers in court in NY trying to argue that federal prosecutors should have essentially zero access to the documents, phones, computers, etc. that they seized from Cohen on the basis that he was the President's lawyer and attorney-client privilege is so important here that none of the material should be examined, it should all be returned to Cohen and the prosecutors should forget about anything they might have seen.
But during the call in to Fox News, Trump himself said that Cohen really didn't do much legal work for him at all. That means that very little of Cohen's material would be privileged as attorney work product for Trump (even if that stood), based on Trump's words there.
If (and we don't yet know for sure) Trump and Cohen collaborated on any number of illegal activities (money laundering, fraud lying to buyers, bank fraud lying to lenders/investors, violating campaign laws in coordinating with Russia for valuable assistance during the election, so-called "conspiracy to defraud the United States" due to their actions related to Trump's candidacy, and others) and Trump screwed up the claim his lawyers were trying to make in court that very day, then we will, retrospectively, say that Trump "incriminated himself" by helping the prosecutors to have access to all of the material seized from Cohen.