To write an NFT contract that allows users to mint their own data into NFTs and share them with companies, you will need to be familiar with the Solidity programming language and the basics of smart contract development on the Ethereum blockchain. Here is a basic outline of how you could structure your NFT contract:

Define your NFT's basic structure: This includes defining the properties of your NFT, such as its name, symbol, and the data that it will hold.

Implement a function for minting new NFTs: This function should allow users to mint a new NFT and specify the data that they want to include in it. The function should then create a new NFT with the specified data and assign it to the user who called the function.

Implement a function for transferring NFTs: This function should allow users to transfer ownership of their NFTs to other users or companies. The function should take the NFT ID and the address of the new owner as inputs, and update the NFT's ownership accordingly.

Implement a function for granting access to NFT data: This function should allow users to specify which companies should have access to their NFT data. The function should take the NFT ID and the addresses of the companies as inputs, and update the NFT's access list accordingly.

Implement a function for checking access: This function should allow companies to check whether they have been granted access to a particular NFT's data. The function should take the NFT ID and the company's address as inputs, and return a boolean indicating whether the company has access.

Test and deploy your contract: Before deploying your contract, make sure to thoroughly test it to ensure that it behaves as expected. You can use a development environment like Remix or Truffle to write and test your contract. Once you are confident that your contract is working correctly, you can deploy it to the Ethereum network using a tool like Remix or a smart contract deployment service like Infura.

Note: This is just a basic outline of what your NFT contract could look like. Depending on your specific requirements, you may need to add additional functionality, security measures, or error handling to your contract.