In my opinion a small gap would be a 1/64" not a 1/16". How it looks is up to you as to whether to fill it or leave it. If you can live with then fine. If you can fix it that's even better. You will learn a bit by fixing a mistake rather than leaving it.... just sayin'
For what it's worth, a fill is not a fix in the strictest terms, it's patch..... Been there. done that a few times. The best fixes as those that are not visible to the uninformed, but known only by the builder.
Finally, a gap that is not structural and only visual and may not even show is probably OK.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
Last edited by woodnthings; 01-09-2014 at 02:18 PM.