I don't think Chopin wrote in a blues styles...these "little notes" can mean many things, depending on the situation. In the nocturne, they mean serve to make that passage a "cadenza," or a metrically free passage which should be played with great expression and rubato, because there is no "accompaniment." Often in Chopin these occur when there is accompaniment, so that just means you try to keep the left hand steady while playing the "cadenza" freely. In op. 25/1, it's a little different, this notation is much less common, but is used to set of the texture from the melody, which is written in large notes.