Future social metaverse applications over 5G Advanced (5GA)/6G will be realized as verticals defined by 3GPP Vertical Application Layer (VAL)/ Service Enabler Architecture Layer (SEAL) service-based architecture. These applications will utilize the services of the User Plane Function (UPF) for efficient routing, which in turn require the services of the Analytics and Logic Function (AnLF) within the Network Data Analytics Function (NWDAF) to provide real-time analytics. Being a logically centralized entity, service disruption may occur due to sudden AnLF failure or congestion. We propose BlockAnLF, a blockchain framework over distributed UPF nodes for secure decentralized storage-cum-consensus of AnLF output policies. Each policy issued by the AnLF is encoded in JSON and stored within individual blocks of the blockchain, a local copy of which is held by every UPF node. The UPFs act as block validators, by creating new blocks and executing a mutual consensus algorithm to commit the latest block. In the unlikely event of central AnLF unavailability, individual UPFs can query their local blockchain instead to receive immediate responses. Experimental results show that BlockAnLF achieves significantly less query time (about 76.34% benefit) as against the traditional central AnLF architecture, as well as providing a secure and immutable policy storage mechanism in a decentralized distributed way. The proposed scheme is aimed at enabling smoother flow for VAL/SEAL packets within the 5GA/6G core for social metaverse service providers.