Could be infected. Visit a dentist

1. Tooth swelling is often caused by Extreme tooth decay . it often begins like a simple tooth ache . 2.swelling can also occur as wisdom teeth attempts to break through the gums . 3.your wisdom teeth usually start to erupt during late adolescence sometimes there is no enough space for them to come out so they are partially out or completely inside the bone. this condition can lead to pericoronitis or inflammation of the tissues surrounding the tooth when only a part of the tooth has erupted into the mouth it can create a flap of tissue that holds food particles and debris and acts as a dent for bacteria in the area between your teeth and gums

Swelling means some infection is there. It maybe due to the blackish discolouration of the tooth you are saying about. The infection may also be due to infection in gums beside the tooth. Share picture of the area, for further diagnosis.

Get an X-ray done. Blackish area is probably the decay. Generally wisdom teeth will need to be removed as it may not be possible to root canal them. Consult a dentist and they will guide you accordingly

Where is it blackish? Tooth or gums? Swelling and pain are often signs of infection, go see your dentist for a check up