Satan was not created a Satan as he is now with the devilish power. For many years he was a companion and associate of the the angels. He misused his position and power, and began to rebel against goodness and truth, and started doing wrong and evil and finally turned to what it is now. On the other hand; SATAN can systematically not harm or seduce a
believer unless he is obeyed. As for those who wish to tread the path of truth SATAN is a means of manifesting, and bringing to action the possibilities and hidden power of man; for evolution always establishes through contraction and conflicts.
So creation of Satan as a Jinn who used to worship Allah for a long time before creation of Adam has nothing to do with Injustice.