More info needed.
Did you ASK him for his opinion about following a particular mehalch?
Why did you ask him and not your rebbe in the first place? Once you asked it isn’t so simple to ignore his opinion.
If OTOH he offered his opinion without you asking then I don’t think you are bound by it if your Rebbe says otherwise. Asking for a brocha from a godal doesn’t obligate you to follow his mehalech hachaim.