Square footage issue days before closing

[Lallu Tappu]

I bought a house about 4 years ago and got an appraisal at around 1850 sq ft. I had recently listed that house for sale at 1850 sq ft. priced accordingly. A week after the inspection was done and repairs were negotiated, the buyers came back and said that they measured the house and it is about 250 sq ft. smaller than said, that it is 1600 sq ft. I looked at the appraisal again and realized the appraiser made a typo and did in fact measure the house wrong. The walls on the lower and upper floors are identical but the appraisal has them differently sized owing to the size discrepancy. 

I wanted to know what is my next recourse and if anyone else has had a similar situation. Since it was over 4 years ago, can we still go back to the appraiser and if so, what does that mean? My realtor says he has never had this situation before and is unsure on next steps.