There are valid medical reasons for using the birth control pill that don’t involve birth control, and therefore it’s use would not be sinful. If one “unknowingly” used the pill it wouldn’t be a sin. If your contention is they didn’t at the time KNOW the church position on artificial birth control, then valid confession and penance take care of that, as to the “temporal affects” of sin, I assume you mean the temporal punishment due for sin…I suggest you read paragraphs 1472 and 1473 Regarding Temporal Punishment due for sin. Works of mercy, charity, prayer, and penance lead to the change of heart that is necessary for the attachement to sin (temporal punishment) to be removed.