This is what happens when a needle which has been in contact with potentially infectious material (i.e. any non-sterile needle) is accidentally (or otherwise) stabbed into someone it was not meant to go into.
A constant risk to health workers worldwide, needlestick injuries have caused many unfortunate people to come down with blood-borne diseases such as hepatitis and HIV.
An accidentally jab with a sterile needle, fresh out of the sealed pouch and which has poked anyone yet does not qualify as a needlestick injury.
Protocols vary from hospital to hospital regarding what should be done after a needlestick injury. Everyone agrees that the needlestick wound should be washed with copious amounts of water and soap. What usually happens after that is that a bunch of screening tests are done on both the health worker and the patient (whose body the needle previously went into) and repeated after 3 months on the health worker to rule out HIV. There may be requirements for notification to the people in charge of infection control and/or the administration.
Getting a needlestick injury is a very serious problem as a lot of anxiety usually arises in the affected nurse/doctor/medical student who typically goes through hell waiting for the laboratory results.