A non-fungible token (NFT) is a non-interchangeable unit of data stored on a blockchain, a form of digital ledger. Types of NFT data units may be associated with digital files such as photos, videos, and audio. Because each token is uniquely identifiable, NFTs differ from blockchain cryptocurrencies, such as Bitcoin.
Bitcoin is been studied by many Islamic scholars in different levels and accordingly different verdicts have come from different scholars while many leading scholars (Maraaje' of Taqleed) have not issued any verdict waiting for information or research.
Ayatullah Sistani did not issue any verdict regarding Bitcoin till now.
There are scholars in Najaf Ashraf and Qom who say that dealing with Bitcoin is permissible as far as it does not violate the law and does not harm any one.
NFT is still under research among many scholars but the problem with it is lack of evidence that it deals with really existing material. Till we hear a clear verdict from an authentic Marja' of Taqleed, we need to wait unless you are sure that you are buying or selling an existing material.
It is must on you to know exactly what are you buying? and you must be sure that all the items are permissible to deal with.