Bootstrap : found problem in adding icon button

I add an " i " element with class = fa fa-thumbs-up within Like button but it does not work, the icon for the Like button does not locate within the button, it is located outside of like button.

Like

<button class="btn btn-block btn-primary"><i class="fa fa-thumbs-up"></i>Like</button>
or
<button class="btn btn-block btn-primary">Like<i class="fa fa-thumbs-up"></i></button>

make it inside the button not outside it so you have to choose one of the two ways above. hope it works for you