If you use the Damm algorithm to generate check digits, is there a method to try correcting the error if the code doesn't validate?
Nope, the algorithm can only be used to detect errors, not correct errors.
This can be demonstrated with a simple example. Let's say that you receive a number containing the digits 9857. When you run the algorithm on that number, the result is 6. So one of the digits has been changed. But which one?
With a brute force search, you can determine that the original number could be any of the following:
original resulting
number error that occurred number
1857 the first digit got changed from 1 to 9 9857
9157 the second digit got changed from 1 to 8 9857
9827 the third digit got changed from 2 to 5 9857
9850 the fourth digit got changed from 0 to 7 9857
So a number that contains an error does not uniquely identify the original number.
In general, it's possible to get a correct checksum by changing any one of the digits. Which is to say that if you receive a number with N digits, and the checksum is not 0, then it's possible to change any one of the N digits to get a correct checksum.