you could wait to see if the IRS bills you. if your taxes are computed using the tax tables there is a $50 range with that same amount of taxes for any amount of taxable income in that range so there may be no increase in your taxes. if you are due a refund the IRS might just take any tax increase out of the refund. if you owed and made payment, the tax increase may be so small IRS won't bill you because it costs more for it to issue the bill and then process the payment than the tax increase.
the $15 from the IRS is because it was tardy in getting your 2020 refund to you. it was included in the refund check.
if this is going to worry you then amend, but you have to wait for your original return to be accepted and then fully processed before you can submit an amended return. don't bother to file if there is no increase in your taxes
