Even if you have withholding, you can be assessed a penalty if you owe more than $1000 when you file (because you did not have enough withheld.)
You can decline Turbotax's recommendation to pay a penalty, and wait and see if the IRS sends a bill for a penalty. If they do, you can request an abatement (forgiveness) as a first-timer.
In the mean time, you need to change your W-4s so you have more taxes withheld. Try the IRS withholding calculator.
https://www.irs.gov/individuals/tax-withholding-estimator
