If the bullet is bulging out the brass a wee bit but you are still taking out the bell mouth needed to seat the bullet in the crimping step and the round fits the chamber, it's ok to use.
It's a leftover from when the sizing step which squeezed the brass back down after firing and squeezed it narrower than original unfired factory brass.
You may also see that there is a slight case bulge near the case head that can't be taken out with resizing if the brass has been fired in a Glock. That's the "Glock bulge." (you can look that up.)
A case gage or barrel check is vital if you are loading for perfect functioning such as for match ammo. I use the bulged ones in a different gun with a larger chamber for practice.
Others may have a different answer for you.