Gap between post content and sidebar

I am extremely new to wordpress, was recently transferred over from blogger and still trying to figure things out. I did not do the tranfer or design myself, had someone do it who is currently out of town and not reachable to help with this.

I’ve done something and created a gap between my post content and sidebar, a rather large gap that was not there before. I want to widen out my post content to connect with the sidebar and remove the gap.

I have gone into the css file to check the width and the width is telling me 550 for post content and 450 for sidebar so I am not sure what the issue is, why it’s showing such a gap.