Hello vaishnavi,

Yes, you can have big nails while going for NEET exam. As they have not mentioned any kind of limitation or rule on body parts. 

They just asked candidate to maintain the dress code i.e a t shirt or shirt along with a simple trouser.

I will advice you to take a nail cutter with you . As if they asked you to cut them. Then you can go for it within seconds.

Hope it helps. 

Thank you :)