I smashed my finger 2 days ago nail is black and it's swollen should I get it drained or wait till the nail falls off I'm in a lot of pain?

Drain if in pain. If the nail is causing you a lot of pain, it's a good idea to see your doc to have it properly drained. The process will involve burning a hole in the nail with a small, hot wire, allowing the collected blood to drain out. Eventually the nail will likely fall off on its own but draining it will release the pressure relieve the pain.
See md. If you are in lot of pain there is possibility of broken finger. A x-ray may be ne essay to rule out a fracture.
Immediate attention. Is needed, go to ER will X-ray to rule out fracture and drain the blood to relive the pain and prevent cut off of blood supply by pressure built up in the pulp space, which may cause bone necrosis due to loss of blood supply. Do not wait see the ER doctor.