Not long ago I wanted to change the permalink structure on a blog where the full date was included in the post urls to one where it was just /category/blog-post-title. The site is on a managed host and they setup the redirects for me and then I changed the permalink structure in the WP settings. Everything worked fine after and all old posts now redirect to the new structure.
However in Google search console I can see that my 404s report has jumped from a few hundred to several thousands but it seems to be counting the urls paths to elements such as images within the old posts permalink structure eg
/2012/6/some-post/some-image-in-post
all the old posts themselves and their content redirects fine though.
Do I need to worry about these 404s? It annoys me to see so many in my reports like that even if they aren't hurting my site