what to do when foot swells in a camwalker and aches around outer edge of foot and instep wearing for non displaced fracture of fibula

Have you tried elevating it as much as possible? That often helps.

Elevate and ice as much as possible.

you might be doing too much. try resting more

If you absolutely can't elevate, loosen the straps until you can so there is more room. But ice and elevation would be the key to counteracting the swelling.