See:
https://forums.developer.nvidia.com/t/jetson-nano-2gb-wont-boot-beyond-nvidia-splash-screen/220018/5
You would lose all content and start “fresh”. You could, however, clone first, and then you’d have a copy of what you started with.
I don’t know if this is always true, but I think startlxde is usually present by default (at least on the semi-older releases). I don’t know what went wrong on your Jetson, but I saw a web search mentioning installing “lxde-common”. You might try to “sudo apt-get install --reinstall lxde-common” (I am just guessing, but it is worth trying).