Does the government ever pay back its debt from the OMO to the Fed? I'm getting confused about how exactly does money being created by the Fed.

From investopidia.com:

The Fed could initiate open market operations (OMO), where it buys and sells Treasurys to inject or absorb money.


If the Fed holds the Treasurys until maturity doesn't it need to be paid back the par? So how exactly does extra money being created?

Thanks
Yes, it does. Maturing bonds held by the Federal Reserve are repaid by the Treasury, just as they repay any other creditor.

However, the cost to the Treasury of doing this is a policy decision of the Fed and can be effectively zero. It’s critical to understand that the Fed’s excess profits are paid to the Treasury. Last year, they paid $54.9 billion to the Treasury. As a result, the vast majority of the money that the Treasury “pays back” to the Fed flows right back to the Treasury. 

To dig a little more into the dynamics, the Fed often decides to reinvest the repaid principal on a bond, so as to not reduce the aggregate money supply (you can think of this as choosing to keep rates lower). When they do this, the actual impact on the Treasury is approximately zero. If they choose not to do so (if they choose to allow borrowing costs to rise), the demand for Treasury debt is reduced accordingly, and the Treasury’s borrowing costs will rise.