Thank you for posting your question here, I will try to answer it to the best of my abilities.
Cortisone is a type of corticosteriod and is ususally given as an immuno-supressant or to reduce inflammation in a person.
As such, I dont know of anyway in which it could've helped with your periods, did the doctor mention why he was giving it to you? Do you have any other problem which you are being treated for? Without knowing the answer to these questions, I cant really say why your doctor gave you a cortisone injection
I hope this answered your question.