What should I do, given that I made a vow to work in the Prophet's Mosque, cleaning it for the rest of my life without pay, and I was saved from a problem, and I am a university student who wants to complete my studies?

A vow contingent on a disliked condition is disfavored (makrooh), but it must be fulfilled when the condition is met, based on the Almighty's saying: "And let them fulfill their vows," and the Prophet's (peace and blessings be upon him) saying: "Whoever vows to obey Allah, let him obey Him." If the one who made the vow is unable to fulfill it, he must offer expiation for breaking an oath.