Hey Akhila!!

Greetings!! 

A student having a permanent tatoo can write exam and allowed to the examination hall as there is no such mention in Admit card of NEET and on the official website of NTA regarding expulsion of the students from the examination due to a tattoo.

Still it is recommended to go to the examination centre early and inform the invigilator and checkers to get approved by them with proper checking to avoid any consequences and delay for the examination as this is the question of your hard work and future.

Good luck!!