If you have ZBrush or access to ZBrush you may be able to salvage the situation.  Ideally, you'd be able to load the original, unmorphed head and then load the "damaged" one as a morph target. If that's something that you can do still, here are the steps:

Load your original head

Go to Tool>Morph Target>StoreMT

Then Load the "damaged" head

Go to Tool>Morph Target>Switch

You should now have the original head again.

Click and hold on the Standard Brush so that you can select the MORPH brush from the popup list of brushes.

Using the Morph Brush, paint only in the areas you want the Morph to appear.

Once done, go to Tool>Export and give the OBJ a unique name. Then load it into Poser as a morph target for the head of your character.

HOWEVER

If the program you were using has changed the vertex order and you can no longer use the "damaged" head as a morph target, you'll need to do this instead:

thanks for this was very useful for me