As already said ... no hard and fast rules as to width.
You might even want to have more than one border.
Even on that small of a quilt it can work.
Plus of course, you can go borderless.
Knowing the block size, does not really tell us what the pattern/design is.
Sometimes that is what really helps us determine what looks right/best for a border.
Totally agree with ThimbleBug ........ starting at the size you have, I would keep my borders so that it would fit on one WOF.