This is (probably) not a problem of your plugin. Google uses crawlers to index every page. What probably happened is that google indexed your page before you were using Yoast. This means it indexed your text from your footer and uses that as a description of your website.
How can you fix this?
- You can just wait until google re-indexes your page, but this might take a while.
- You can try an make google to re-index your page. This question has covered that already: How to request Google to re-crawl my website?.