Is it permissible to retract a vow in which one said: "I vow to You, my Lord, that I will not supplicate You for anything other than this matter; only fulfill it for me"?

The supplication of asking (Du'a al-Mas'alah) is obligatory or recommended, and it is not permissible to abandon it, contenting oneself with God's knowledge of the servant's condition. For the prophets supplicated to God extensively, and the sacred texts command supplication. Abandoning supplication angers God, and in it there is faith in God's power and a declaration of His oneness (Tawhid). As for covenanting with God, it may be a vow (nadhr) and an oath (yamin) if it is an act of closeness (qurbah), or merely an oath if it is not an act of closeness. If one fails to fulfill it, an expiation for an oath (kaffarat yamin) becomes obligatory. You should turn away from that covenant, and instead turn towards supplicating to God, and perform the expiation for an oath.