I can barley tighten my fist or turn the door knob because of wrist pain, what's going on?

Depends on cause. Thee are a variety of causes of wrist pain ranging from ligament tears tendinitis arthritis to fractures. An examination by a hand surgeon or orthopedist and a simple xray can usually make the diagnosis to suggest treatment.
Many possiblities. Wrist pain has many etiologies from simple tendinitis from overuse, to inflammatory joint conditions eitehr from arthritis, infections, or autoimmune, to trauma both old or new that can put the wrist mechanics into disarray. This differential can be narrowed down by a qualified medical professional evaluation -.
Any number of things. It depends on whether your wrist pain is due to a joint, nerve, circulatory or muscle problem. It could be a systemic, not local cause. See your doctor if the pain persists for more than two weeks.