The officer used his leg to flip the man onto the floor before he exited the cell, which the authority found to be unnecessary.
Tairawhiti Area Commander Inspector Sam Aberahama said any use of force was a last resort, however the offender presented a risk to the officer and others in the station.
"The officer involved took reasonable steps to quickly detain the man after he became aggressive," Aberahama said.
"The challenge for police is when there are levels of resistance, the force applied should be reasonable and proportionate.
"It is important that we review incidents such as this and share anything learnt with each other."