I'm sure this is probably an incredibly stupid question but I pressed the small X on the tools on the left and I have no idea how to get them back. If anyone could tell me how it would be of great help. Thanks!

Goto the right-most button on the top toolbar. Click on it; a drop down palette will be shown. Select the item labeled "default".

It's weird though that here the toolbox doesn't have a close button. I wonder whether that's dependent on the widget theme.