I assume you want something like the following:
An HTML output could help us to understand the issue more clear. However, you can set the position of the parent to relative, using:
p.your-p-class {
position:relative}
Then, position your button as absolute.
.pin-it-button{
position: absolute;
top:-50%;
left:50%}
This will set your pin halfway from top and left, which would center it on your image. Depending on your pin’s size you might wanna reduce the percentage a bit.