Hello Sanjay yadav r , If there's anything wrong with bubbling then your paper will be rejected. It was informed many times at official website as well as explained by faculty, that there should be no mistakes in OMR sheet.

So, Its 99% chances to rejection of your OMR sheet but there is 1% chance or hope  by the person who can accept your written roll number.

Hope it will be helpful for you :)

Dear Student,

Don't worry your result will be announced and it does not cause much problem as you have written correct roll number but bubbled wrong it will not read by machine but the team who will be checking your paper is already aware of this issue and manually check if somethimg is wrong as it can happen with anyone so they will take care of this issue.You can contact NTA if you are worried.Below is the email message them with your query

neet@nta.ac.in