Can a chiropractor really help with vestibular disoder?

Unlikely: Vestibular disorders typically need to be addressed by an ear nose and throat doctor or a neurologist. A chiropractor may make you feel somewhat better but will not address the underlying problem.

Not hardly: What did he tell you, that it's a "pinched nerve"? He'd have said that no matter what you had: Ulcers, ovarian cysts, insomnia, anything. That's the delusion of chiropractic: Every problem is a pinched nerve: Not just vestibular disorders or back pain, but everything: Depression, infertility, acne, constipation, obesity, flat feet, you name it. You're being sold quackery with a capital Q.