Hello! Thank you for the query. Such bruise is quite common thing when during intravenous injection, the vein gets ruptured. Due to vein hole, blood gets out of it and appears under the skin. Such bruise in most cases does not need medical attention and heals by its own. It just takes quite long time which can be a week or even two. However if in bruise area redness, pain, swelling, tensed skin appears, fever is present, you should contact a doctor as it might be an infection. If no such symptom, try to elevate your arm from time to time so the bruise can be cleared quicker. Hope this will help. Regards.