How long will it take for my black eye to heal?

1 week. Usually it takes a week. You can apply an ice pack, 10 minutes on/10 minutes off. You can also use arnica gel, a homeopathic remedy [apply carefully because it's near your eye].
Up to 2 weeks. Don't be alarmed if there is still some bruising at 2 weeks. If you are older, you may see the bruising "sliding" down the cheeks. This is also normal. If you have persistent deformity after swelling comes down, double vision, or other serious associated complaints, go see a facial plastic surgeon to make sure you don't have any fractures.
Up to 2 weeks. Sometime bruising can last 2 weeks. Especially in older patients the bruising may 'slide' down with time. You can of course wear make up to cover it if desired. If there is any associated deformity after the swelling comes down or you have any vision changes get it checked out if you haven't already.