A: If this is a standard drywall material around the window, I would open the crack approximately twice its size (if a hair line crack), then mix up some 20 minute drywall compound (or use pre-mixed) and apply it into the crack with my finger, using slight pressure. Prior to the mixture hard setting, use a clean damp cloth and wipe down the wall to get rid of any lines or marks from the over fill and allow the existing texture of the wall to bleed through.

The other alternative, if this occurs repeatedly, would be to apply a paintable caulk that is also water washable directly into the crack, again with the finger. Before it sets (usually within 30 minutes), wipe down with a clean damp cloth, again to smooth and to allow the existing texture to bleed through.

Small drywall holes

Widen small holes and cracks in drywall with a sharp tool. Push the drywall paper covering in to prevent ridges within the patching. Fill the holes and cracks with a spackling compound. Some cracks may require more than one application. After the compound has thoroughly dried, sand with fine-grit paper, then prime for painting.

-- Tips courtesy of HomeAdvisor.com