There is some information here on how the NINO is constructed and why there is a suffix:
National Insurance Numbers (NINOs): Format and Security
Although it is still part of the NINO, if it is quoted incorrectly it would not have any impact on the NI record.
Many (although not all) HMRC systems will accept the NINO in the form of the 2 prefix letters plus the 6 numbers and no suffix at all.
If you think that the incomplete year is incorrect, you will need to write to us or call the NI helpline.