Restore small section of OSB behind inner wall
When I have a small hole in a wall I will use a strip of wood (1x1/2x~8”). Slip the piece into the hole and using screws. Put at least 1 screw in each end of the board. I put one on each side of the hole then put the piece in and screw the square to the strips I just installed. I have even used paint stir sticks when making this kind of repair in drywall, but for plywood or OSB like something a bit stronger. I have used silicone on the wood to seal the patch at the seams. This would be the best advice I can offer with the information provided.