Erm i am having a dark spot or a big black dot under the toe of my left foot. it is really big and almost about 1/3 of the toe. what should i do?

Get it looked at by : A doctor it could be a plantar melanoma. If not treated it could be trouble. Might be nothing but a black spot on the bottom of the foot we always have a high suspicion for cancer, especially in an dark skinned individual. A similar thing was the demise of bob marley.

Hematoma.: It sounds like a subungual hematoma- often caused by badly fit shoes or trauma to the nail runners frequently get these and the nail will sometimes fall off. If you are anxious about this or it is causing pain, see a podiatrist for further evaluation.

See a podiatrist: This could be many things & best examined and treated by a podiatrrist.