I don't think this is particularly hard as it is confusing.
What is this store you're running? Did you start your own business? Or are you the manager of a store owned by someone else? You are not being clear here. Because the very simple answer is this: if you did indeed start your own business - then this is something you are NOT meant to do on a PGWP or a conventional work permit. The only rights you have are to work, not start a business. If you have indeed started a business of some shape or form, whether as a registered or unregistered business owner, you have violated the terms of your stay in Canada and you're in trouble.