What is the religious ruling and what should a young man do who has repented to Allah after having been alone with his fiancée, whom he had promised to marry, then the engagement was dissolved and her guardian came to know what had happened?

The suitor erred by transgressing God's boundaries. The fiancée is a non-mahram to him; it is not permissible for him to be in seclusion with her, touch her, or speak with her merely out of desire. Rather, his conversation with her should be for a need and a legitimate interest, within the bounds of modesty and seriousness.

The man must repent to God by abandoning the sin, regretting it, and resolving not to return to it, while keeping away from its causes, and concealing his own actions and those of the girl.