If you're sure that specific URLs should not exist on your site, 404 errors won't hurt your search performance, and you can safely disregard them. It is crucial to ensure that these and other invalid URLs return a proper 404 HTTP response code and are not blocked by the site's robots.txt file.
Here are some guidelines for dealing with 404 errors:
Remember that submitting a URL removal request using the URL removal tool will not eliminate the error from the report. Additionally, issuing a 300-level redirect will delay the recrawl attempt, possibly for an extended period. If Googlebot encounters an unexpected URL, such as a URL generated by JavaScript or Flash files, it may produce a 404 error in the Crawl Errors report. Still, this error should not affect your site's crawling or ranking. Google is working to prevent this type of crawl error.