Just let it flash out good will be fine. Of course this depends on how much you got on it. If we are talking a filler on a hood and you spilled the gallon can on it with the whole gallon running across the plastic filler onto the floor I would say remove it and redo the filler. But if you were simply wiping with a wet rag and you wiped across the filler, don't sweat it. Let it flash out will be fine. A light sanding with the same paper you had previously sanded the filler with "opens" it up to flash better.