I was exploring Skyrim, so I was walking around, and I happened to come here by falling through a hole in the ground. I'm just level 3, so is there any way to get out of here alive? Or do I have to restart the game?
You can always lower the difficulty settings (and revert it back later) when you're having a hard time on a particular area or quest.
Also, see the UESP wiki article about Geirmund's Hall for a walkthrough and tips on how to navigate and get out of that area.