Why can bruising take nearly a week to appear is it normal ?

After 2-3 days: Contusions from injuries may not present for 2-3 days after the incident. Continue to monitor if it's just a cosmetic issue. If you have any new symptoms (tingling, numbness, or weakness in your arm), then see your physician. http://www.nlm.nih.gov/medlineplus/elbowinjuriesanddisorders.html

Very much so: Depending on how significant a bruise you have it may even take longer than a week to resolve.