There is a painless dark spot between my teeth. what should i do? is this bad?

See a dentist: Decay is a slow process and may be painful, need to have an xray taken and see what it is.

Difficult to tell: Without seeing the dark spot, we can tell you the possible causes: decay, long standing dark tartar, gum recession leading to a dark space, discoloration of tooth structure from an amalgam filling, traumatic injury, to name a few. See your dentist for a thorough evaluation to determine if you have a problem and what the solution should be.