Do I need to add a current limiter to this battery pack I'm making?
1.5 volts per cell suggests that your batteries are alkaline chemistry.  You're just discharging a battery through a motor.  So, you probably don't need a current limiter.

I suggest adding a fuse between the battery pack and the motor.  If the motor fails and becomes a short circuit, the fuse will blow and cut off the battery current.  Motors usually work better with slow blow fuses (as opposed to fast blow fuses).

As an experiment, connect the ampere meter between the battery and the motor.  See how much current actually flows.