And as a practical matter, it doesn't really clarify the pronunciation of Nguyen unless one knows which English pronunciation of ng you're referring to. I'm just teasing with this pedantry, of course; I understood what you meant. But then, I already knew how to pronounce Nguyen.
What are bruises? Bruises are bluish or purple-coloured patches that appear on the skin when tiny blood vessels, called capillaries, break or burst underneath. The blood from the capillaries leaks into the soft tissue under your skin, causing the discolouration.
What you should be asking is how soon will the bruise appear or become visible. To expand on Alan's point 4, Force of the blow and position, the force is quite important in that a heavier blow will typically cause more bleeding, leading to a larger/darker bruise.