If my skin is going to hyperpigment after getting a Vi peel, how soon will I know?

It sounds like you are having normal peeling. However the post peel protectant commonly stings during the peeling process. I advise my patients to discontinue the use of the post peel protectant and use a thin coat of plain old Vaseline instead. Rule of thumb after a peel is to stop using anything that "burns" when you put in on. The inflammation caused from the irritating product can cause hyperpigmentation to occur. It is too soon to see evidence of PIH at 3 days post peel. It usually takes 1-2 weeks before it is visable. Make sure you use a good SPF with Zinc Oxide and Titanium Dioxide in it at ALL TIMES and avoid the sun as much as possible while peeling! Your post peel kit should of included an SPF in it.