Hole in wooden sash window needs repairing

Hello, I am looking for a quote for repairing a minor deterioration in one of the sash windows in my property. A small piece of wood has fallen off from the sash leaving a hole in the wood. The hole has not comprised the integrity of the window and the glass is still firmly in place. The window is still structurally sound and functional, so it does not need replacing or restoring. I would expect that the repair will only consist of filling the gap with wood filler and painting over it. Could you please let me know how much this would cost to repair? Thanks, Myriam