The thing is I lost my seed phrase for MetaMask wallet. Luckily I had also backed up my private key. Is it possible to regenerate my "seed phrase" from my private key? It would be great if I could do it offline on my local computer because I don't want to share my private key on any online website.
I guess you can not generate seed phase from private key. But private key is everything for your account. So if had multiple accounts with some balance and you remember private keys for all addresses, then you are a lucky man.
If this is the case, you can simply create new account in metamask and get a new phrase. And then you can import your accounts to your metamask wallet using private Key.