The Stress, Normal to Core result shows the value most cavity pressure sensors report as the "cavity pressure". While the polymer is molten the stress value is very close to the cavity pressure but when the polymer is frozen and the mold (core) has a significant elastic deformation then the value may be significantly different from the pressure result.
Use this result along with the Pressure result, to see the effect of the mold elasticity on the values when validating prediction of the experimental cavity pressure results. High local normal stresses caused by the core elasticity can also cause some cracking in the moldings if the plastic is brittle
You can also use the Stress, Normal to Core result along with the Residual Stress result for the prediction of cracking.