How to stop Images in Posts Bleeding over Sidebar?

Some images in my posts are able to bleed over the side bar, I am using Modularity as a theme, what code can I add to hide that part of the image that bleeds over.

i am under the influence it has somethingt to do with Overflow: Hidden?

my site is: https://www.andredeveaux.com

I want my images to not bleed over my layout/sidebar like on my other site https://andredeveaux.wordpress.com