See in general its not a severe discrepancy of information which can lead to cancellation or any severe cases against you. Although its better to have all the things neat. You are preparing for NEET and if you get a seat in medical college then why will you want to take any chance which can harase you in the time of admission. Its better to keep no probability.

Now you can do one thing that you can get a attested copy of the document from any gazetted officer (better for you if you do it from DM or SDO) or you can apply for rectification, the procedure of which you can get from the DM or SDO office.

I hope this helps. All the very best for your future endeavors!