Of course, private key of Metamask wallet is important. This will further strengthen the security of your wallet.
also how can i get key back , i am sure there would be some way
You have already received many suggestions in this regard. I'd like to add a little more. If you are an Android mobile phone user, first click on 'Setting' - then 'Security & Privacy' - then click on 'Show Private key'. Now you can see private key of your Metamask wallet.