Hole in the joint of wall

There are a few ways to fix it, although the description is a little lacking to be fair, adjoining photos would be more helpful. Could use a wire mesh plaster patch. Or could also use some spare plasterboard with scrim or string attached, to fit through the hole and add plaster or gripfill so it sticks behind the hole (using the string to pull the board gently towards you while the adhesive dries). Once dried, use filler to fill the hole.

You mark out with a pencil and small leval, a 4 center meter x 8 center meter oblong. Then cut it out with a Stanley knife. It should be plasterboard. If its lath and plaster, use a jig saw on slow speed. Then cut a pice of plaster board the same size. I find ply the best.! Cut a strip 5x8 cn. Put a long dry wall screw in the middle, pass it through the hole pull the screw and turn the ply, then screw on each side, take your screw out your holding. Then fix the pice of board in the hole screwing into the ply, scrim it on both sides. Then dry wall filler over the scrim, feather it out, let that dry, then feather it nicely with dry wall finish could be 2 coats. Let dry, then sand so it's blended and smooth with the wall. Good luck.!

Cut a plasterboard square 10cm×10cm Place it on top of the hole make sure the hole is in middle drow pencil line all around the square plasterboard than cut it with pad saw. Take 15 cm timber and pass it through the hole ether vertically or horizontally doesn't mater and make sure is no cable to screw into By holding the timber screw into plasterboard and timber both sides .place the square plasterboard in the hole you cut it and screw it into timber, Fiber glas mesh all around than filler, let it dry ,send it ,paint it. Short way ,expanding foam fiber glass mesh filler.(not recommended.)