If fermentation is complete I wouldn't worry, but an excess of star San could slow down your fermentation if you are racking out of primary and fermentation is still active.
Starsan is an acid based sanitizer so it won't hurt anything. I have heard rumor that it can impart a mild taste; however, have never had that issue (in beer). I generally try to get most of the suds out, but don't worry about leaving a little behind.