Piekiełko is part of the town in Mława in Masovian Voivodeship, east-central Poland. Until 2004 it was a village in the administrative district of Gmina Iłowo-Osada, within Działdowo County, Warmian-Masurian Voivodeship. It lies approximately east of Iłowo-Osada and south-east of Działdowo.