Eth appeared in my Metamask wallet, it is not mine

I setup a new metamask wallet a few days ago, created a bsc chain etc,
after doing my first couple transfers with bnb i noticed that there is eth in the ethereum mainnet part of my wallet, this is not mine, and when i look on etherscan i can’t see a transaction related to this eth. The amount was approx $750 give or take the fluctuations, and it is now down to about $23.
Does anybody know if this is a glitch of some sort, is my wallet already compromised?
Any help greatly appreciated.