If NMSC told you that you can submit your score this late and still qualify, then that is their prerogative and I’d recommend you submit the score ASAP. You may not be eligible for the $2500 award, but if any of the schools that offer large school-sponsored awards to Finalists (UKy, Alabama, Oklahoma, etc.) are of interest to you the “benefit” can be well in excess of $100K.
Other than the cost of submitting your score to NSMC…what do you have to lose? Even if you’re shooting for schools that don’t offer anything to NMFs, it certainly couldn’t hurt to have a guaranteed full-ride or near full-ride scholarship safety school in your hip pocket. Just one man’s opinion.