The vow you have taken
is lawful. You either have to fulfill it or break it. However, if you break it, you have to offer Kaffarah (expiation) for breaking an oath, which comprises feeding or clothing ten needy persons, or freeing a slave. If you are unable to do either of these things, you have to fast for three days.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.