One way to repair it is as follows :- Get some lining paper the same
thickness and soak it in wallpaper adhesive apply it over the damaged area
and let it soak in for 20 mins with a very sharp blade and cut a square
larger than the damaged area and remove the excess peal pack the square that
if left and use blade to prise out the area inside the cut square and
replace patch. when it is dry if you can see the cut fill it with fine
filler and lightly sand with fine sand paper.
Mike S