While ascending, the air in your lung expands. If it can't go out your mouth/nose, then it expands your lungs or is forced through membranes. Either way, the results are not good.

Nitrogen narcosis is another risk of SCUBA diving, but it is not really related to breath holding.

Lung over expansion issues can only happen when ascending after breathing compressed gas under pressure. That isn't a problem with breath hold freediving.