To get back to the original question...
Neyjour, on looking as closely as I can at your pic, is the material intersecting the body around the neckline? 'Cos if so, that's the cause of the holes...

It looks like it is, no doubt as an attempt to add the illusion of "thickness" to the material.

The trouble is displacement only moves the surface geometry. it doesn't compensate for edges ..
I can't think of a quick'n'easy solution just now, but hope that what I've posted gives you some insight into the actual problem...

Cheers,
Diolma