I have tiny little black bugs in my bathtub possibly coming out my bath drain how do I get rid of them

Heat a teakettle of water then put a few drops of dish soap or shampoo in the drain and follow with the hot water.

Can you post a pic or describe them more fully? Identification is the first rule of pest control.

I forgot, hot water then cold water. Most small forms of life including bacteria can't live with a sudden sharp temperature change like that. The soap is to wash their little carcasses down the drain.