Yes, you can. One of the requirements for entrepreneur visa is that you must have a registered company. After registering the company, you might consider staying in Hong Kong using the current visa. Visit the immigration department to check for how long your current visa allows you to stay in Hong Kong.
For example, visa allows Australians, Americans, and Austrians to mention but a few, to stay in Hong Kong for up to 90 days. However, if you are looking forward to using the entrepreneur visa to stay in Hong Kong, you will need to wait until the processing is complete.