Is it best to do needle drainage for subungual hematoma or to let it heal on its own?

Drain it.: These things hurt terribly. I don't use needle drainage: too slow and painful. I use a heated (to red hot) bent paper clip to puncture the nail. Takes less than a second and the relief is instantaneous. There is no pain from the heated paper clip. Looks barbaric but works well.

It depends: How much of the nail has the blood under it and if it is painful.