It is must necessary to mention left thumb impression on neet admit card before going to exam centre.If there is any injury on left hand thumb, student permitted to mention right hand thumb impression.But, this doesn't  lead to rejection  of your exam.If u have any doubts just consult to below provided link.

Hi Varapooja,

Don't worry ,  If you have provided all the details correctly then nothing will happen and mentioning thumb impression on your admit card  this will not effect you anyway and also it doesn't effect your marks nor your rank , so don't worry

Hope this information is helpful and for more information click  on below link

https://medicine.careers360.com/articles/neet

ALL THE BEST