Facebook share Thumbnail is wrong

I have everything going good mostly, thanks to you guys. One last thing (OK it may not be the last!) that’s bugging me is I have a Share widget in the sidebar, and when you click the facebook button (when you’re on the homepage), it comes up with this old thumbnail of a pair of wedding rings that I totally deleted from my media library. Other pages may not have a thumbnail (when sharing to facebook) at all, which is no biggie. I just want to get rid of that wedding ring image. Thanks