If you look at the URL when you share on facebook you will see it looks like this:
https://www.facebook.com/sharer/sharer.php?u=http%3A%2F%2Fradiotounsi.com%2F%3Fp%3D1356&t=Notre+Dame+de+mots&s=100&p%5Burl%5D=http%3A%2F%2Fradiotounsi.com%2F%3Fp%3D1356&p%5Bimages%5D%5B0%5D=http%3A%2F%2Fradiotounsi.com%2Fwp%2Fwp-content%2Fuploads%2F12910346_250190685330125_485082804_n-2.jpg&p%5Btitle%5D=Notre+Dame+de+mots
As you can see the images parameter points to:
https://radiotounsi.com/wp/wp-content/uploads/12910346_250190685330125_485082804_n-2.jpg
Which is the correct image for the post, so most likely Facebook has cached the image for your post.
You can try and force FB to pick the right image by using an OpenGraph plugin like Yoast SEO, more details in the FAQ page specific for this issue called “Facebook is not showing the correct title/description/thumbnail, what to I do?”
