Hi JyotiRanjan,

I hope you have seen, whenever you have submitted any application form, you have to upload 3 things:-

• Passport size photo
  
• Your Signature
  
• Left/right Thumb Impression.
  

All these documents are taken in order to check your authenticity. 

On the day of the exam, you are asked to carry your id proof, so that invigilators can match you and your face.

You must have seen, they take your thumb impression and signature in a separate attendance sheet. These Invigilators can match your face and signature but cannot match your thumb impression. These information are matched later on while evaluation of papers. The not matching of thumb impression might create a problem then. Your paper will be cancelled and while checking your result, you would not be able to see it.

In the exam hall, it will not create a problem if that's not very obvious.

Hopefully this helps.