Should one do anything after having paid Zakat on money that did not reach the Nisab, based on incorrect information?

Zakat (definition) is not obligatory on money unless the wealth reaches the minimum threshold (nisab (definition)) and a full year (hawl) passes over it. Disbursing it before that is considered a supererogatory charity (sadaqa mustahabbah) and does not fulfill the obligatory zakat. That charity cannot be counted towards the obligatory zakat, because it is not permissible to hasten zakat before possessing the nisab.