As long as you are planning on making the bow a stiff handle that knot will pose no problem at all, it will add character!
Even if it was in the bending portion of the limb, as long as you leave enough wood flowing around the knot and don't gouge it out too bad it still won't pose a problem. With hickory most of the time you can work the knot as if it wasn't there because hickory is tough wood.
I've got a knot about the size of a quarter in the dead center of one limb about 6" from the fades in the second bow i've made (hickory). I over built the area (left some rings around it), and it's stiff and doesn't bend hardly at all in that area and my bow is still shooting after thousands of shots. However it's performance isn't spectacular (it's 43# at 28"; 40# at my 27" draw and throws a 560 grain arrow (14 gpp) 133 fps on average)