Unfortunately, it's going to take rather a lot of manual painting to fix damage like that. To begin the process of repairing it, you need to reduce the effect of the damage, since I don't think it will be possible to remove it completely in one step.
One method might be to create a curves adjustment layer, fill the mask black, and paint in the curves adjustment using white on the mask. Obviously this is only a first step, further manual repairs will be required to fix the edges between the painted adjustment and the undamaged parts of the photograph.
For example:
Once the majority of the damage has been removed, it's possible to create a new layer - a copy of the visible layers (using Shift+Ctrl+E), and then begin to do more detailed repairs on that, perhaps using the Spot Healing brush.
For example:
