Dear Kirmita,
It is not related to any drug your dad used. It is actually a common finding in MRIs and it is unlikely to be the source of any symptom.
This cysts only grow after minimal bleeding inside usually after trauma - causing water to migrate into the cyst by osmosis- in this rare situations they can cause symptoms.
I am only a layman, but see a lot of questions on this type of cyst on the patient forum. They are usually present at birth and can grown slowly over time. Depending on location, they may or may not cause side effects and make sure you get a competent surgeon for removal.
As for father's drug use a cause... you would have to search in pubmed, but I don't know of a link.