Drill the nose flat out as mentioned, deep enough for the point to not 'bottom out' & see if the bullet ogive is contacted by the punch. If so, it will tend to be somewhat self-centering and may work OK if you have the bullet reasonably started straight in the case mouth.
If not, or just because you want to, you can coat a bullet nose with a little cooking oil and mix up a small batch of epoxy. Put the epoxy in the punch and with the bullet sitting square in a case mouth, run it up & into the punch. Let the epoxy set & you have a perfectly fitted nose punch.