How to Fix Contact Import Errors and Prevent Future Issues

Oops - I imported ~50 new contacts to an existing table from a "Find More People" Search, and then I clicked on the contacts and tried to map the name, to the existing Name column. I didn't realize this would apply to the entire list, and now the rest of my list has an empty first name column. Is there a way to undo this or do I have to re create the table? For context, the original results before these 50 were added came from a Write to table enrichment. Also, what should I have done next time to avoid this error. I guess keeping them separate, creating a new column and then merging the two woulda solved this 😞