Technical terms like "circular thingy" are just a little vague, Justin.
Anyhow, you say the needle didn't move. As long as you have it open, can you carefully move it carefully?manually? A toothpick or bamboo skewer should be safe. It has a hairspring to move the needle. Take a close look a the spring to see if it has a crossed coil caused by a bump.
To clean the battery connector I use a fiberglass brush or pencil eraser.

You don't mention whether you have an Ohmmeter. If you do you can check that the photocell changes resistance as you point it to and away from a light source. If it does then.....
Clean the switch contacts with the edge of a dollar bill or very fine sandpaper or contact cleaner.
If nothing has worked so far you can resolder all the contacts in the unit.