And for next time, it’s best to use a CSS snippet to alter the look of Obsidian instead of changing the theme’s CSS file directly.
In addition to the above link, here’s what the Discord bot says:
Custom CSS lets your completely customize how your Obsidian looks.
To use a custom theme created by our community, go to Settings > Appearance. From there, you can choose among a list of community themes.
You can further customize the look of Obsidian by using CSS snippets. To create a snippet, go to Settings > Appearance > CSS snippets and click the folder icon. After saving a CSS file to that folder enable the snippet in the settings.
We recommend editing the CSS file using something like Visual Studio Code or Sublime Text to properly highlight and format it, as invalid CSS will not work.There’s a wonderful guide on our forum that should get you comfortable with working with CSS, if you’d like to make tweaks yourself: https://forum.obsidian.md/t/getting-comfortable-with-obsidian-css
You can also borrow from existing snippets the community has developed over time here: https://forum.obsidian.md/t/meta-post-common-css-hacks