Is marriage sufficient to expiate the sin of lustful kissing before marriage, and what must the perpetrator do to attain forgiveness?

Kissing one's fiancée before the marriage contract is forbidden (haram) because she is still a stranger (ajnabiyyah) to him. Whoever commits this act must repent to Allah by abandoning the sin, regretting it, and resolving not to return to it. He should also increase his good deeds. Furthermore, he must not publicize his sin.