It is obligatory to stay in Muzdalifa until after the time of Fajr. Based on compulsory precaution, the pilgrim should stay there from the middle of the night until the spread of the light after Fajr that allows pilgrims to see their way, but it is better to stay until after sunrise.
If the vow (“nadhr”) was correct based on religious laws, then it is obligatory to act upon it, i.e. you are not permitted to ignore it, and you must perform the ziyarah this year.
