Hello,
Kudos to you for being so honest and open with your tax obligation!
With regards to your message, you should be able to just re-file last years FBAR when you file this years (both can be done vie the FINCEN e-file system). Just send in two years instead of one.
However, I will mention that the most important part of FBAR is the "disclosure"...not the exact balance of the account. As such, the fact that you already field a timely report, and let them know about your account, satisfies the FBAR requirement. If the actual balance is a bit off, there is no need to worry as you are not taxed on these funds.
In the end the choice is yours, however I think you will be just fine leaving as is and filing correctly moving forward.
Good luck!