Expected penalty?

I have am a US citizen with a 1-year, 60day duration, multiple entry visa. I have been exiting/entering at the proper times over the past months. I just realized however that this time I mixed the dates up and have overstayed by a week. I am worried I will not be able to re-enter after exiting as I have in the past. It seems like a fine will need to be paid (no issue) but I want to know what else I can expect.