Does the effect of a love spell I cast on someone become nullified after I tell them about it, and if not, what should I do to get rid of it?

You must offer sincere repentance to Allah Almighty for engaging in sorcery, as it is a grave sin. Allah forgives all sins for those who repent, believe, and perform righteous deeds. It cannot be definitively stated that thecery's effect is nullified merely by confessing it, but supplicating for its nullification is a good thing. The young man can be directed to some lawful ruqyah practitioners to dissolve the sorcery through ruqyah. It is not permissible to dissolve sorcery with sorcery of its kind.