SIOUX FALLS, S.D. (KELO AM) - A Sioux Falls woman may lose her finger after she tried seperating her son and another man as they fought in her South 3rd Avenue apartment early Monday morning.     Officer Sam Clemens says 51-year-old dwayne Carlton Smith, the 42-year-old woman and her 18-year-old son had been drinking.     Clemens says Smith and the son got into an argument that led to a fight.     The son was holding Smith down, mom tried pulling him off and that's when Smith bit her finger down to the first knuckle.     Clemens says the woman was taken to a hospital but her doesn't know if the finger could be saved.     Smith is charged with aggravated assault.