What do I do if I filed before receiving a 1099-INT? (I was unaware I was receiving one from opening a bank account). In the amount of $200.

[JohnW152]

If your return hasn't yet been accepted by the IRS, wait to see if it is accepted.  If it rejects, you'll be able to amend your return to include your missing information.

If your return has been accepted by the IRS, you’ll need to file an amended return to reflect the change you need to make. 

You should wait to file your amended return until you get any refund you may have coming from your original return.  Even if your original return has been accepted by the IRS, it's still possible that the IRS could change your refund or balance due on that return. 

Please see the TurboTax article How to amend (change or correct) a return you already filed for additional information.

[desmafeather]

I was accepted. 

[TomK2023]

As JohnW152 stated earlier, wait until the IRS has processed your return  and sent your refund before amending your return to include the 1099-INT information.  The IRS may make the correction for  you.  

If you used TurboTax Online, simply log in to your account and select “Amend a return that was filed and accepted.” If you used our CD/download product, sign back into your return and select “Amend a filed return.”

Please note: Amended returns can take more than three months for the IRS to process.