Unlike cryptocurrency, there are no charts to tell how much exactly your NFT is worth at a given moment. One Bitcoin is exactly the same than any other of the Bitcoins in the world (it's a fungible token) but NFTs are unique or limited edition. Similarly to an art piece or a tradable card, an NFT’s value is based on what a buyer is willing to pay to acquire it.
This can depend on a number of factors including scarcity and capability - if an NFT is rare and has additional capabilities (such as access to an exclusive group) its price will likely be higher than a common NFT with no additional perks.