My big toe is throbbing and extremely sore and the nail is all black. should i go to a doctor or what should i do?

TRAUMA?: Sounds like you really bumped/hit it, but you didn't mention any. If you did, and it hurts that much, you should get an x-ray.

Wait and see: If it is after an injury it will usually resolve on it's own. If i is too painful, blood can be drained from under the nail. This can be done in any treatment center. If it is not an injury Dermatology consultation would be advisable.