If someone assumes Ihram by making a vow at the train station in Madinah and is then required to commit one…

If someone assumes Ihram by making a vow at the train station in Madinah and is then required to commit one of the prohibitions of Ihram, such as seeking shade, what is the ruling? What is the way out of this situation? If it is not permissible, is this ruling based on a fatwa or obligatory precaution, and is it permissible to follow another jurist in this matter?