All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
This action does not invalidate the prayer. Standing on one's toes does not undermine the validity of the standing position in the prayer. Hence, your prayer is valid if your heals do not touch the ground in prayer for the mentioned purpose (to remove the skirt from under your feet).
Allaah knows best.