My problem:

I’m trying to create a filter that will add the featured image of a post to the_content, so that I can have the first paragraph of the_content displayed before this image.

What I basicly want to achieve:

<p>First Paragraph of the_content</p>
<img>The Post's Featured Image</img>
<p>The rest of the_content</p>

I someone is able to help me.

Thanks in advance!