Needing to correct an error made in previous year after entering 2 months of data in our new year


We have completed our year end, moved our systems forward, entered about 2 1/2 months of data into our new year. After this we found we had an error at the end of our previous year that has to be corrected. We went back and corrected the error in the previous year, now we are ready to re open our new year again. (Backups have been done on all information entered)
How would the revision to our previous year affect the new years data that has been entered?
Would opening the previous year alter the 2 1/2 months of data we have already entered?
What would be the best way to import just that 2 1/2 months of data for our new year (if needed)?

Many thanks in advance :)