Is anything incumbent upon me if I swore to fast a full day upon committing a specific sin, then I committed the sin and fasted, but broke my fast two hours before the time of Iftar, knowing that the oath was to fast for one day only and not every time I commit a sin?

If a person swears to fast for a day if he commits a sin, and he commits it and fasts, then he has not broken his oath and no expiation is required of him. If he commits the sin a second time and does not fast, no expiation is required of him. A Muslim must avoid sins and repent sincerely from them, and seek Allah's help to avoid repeating the sin.