One option for you. In the outermost container of your widget, you can apply a negative margin that should cancel out the tecton applied margin:

So in this example it would look like this in the widget html / css:

<div class="widget-container">
	<div>Q2 Account Group Widget Content</div>
<div>

div.widget-container {
    margin: -15px;
}

I hope that helps.