Hi,
It seems like that the GPU is acting up and it's thinking that there's an external monitor connected to it. Please do try these troubleshooting steps that may help.
- First, connect an external monitor again and if it will display on the external display press the Windows key + P at the same time and select "Computer Only".
- Once the display is back on the built in display proceed with doing a clean install of the graphics card driver.
- Go to Device Manager and uninstall the Nvidia graphics driver.
- Next is to open Programs and Features then uninstall anything related to Nvidia.
- Once done, download and install the latest driver.
- Here's the link: nvidia.com/Download/index.aspx
- Reboot the laptop once the latest driver has been installed.
- And if the same problem will persist I would suggest taking it back for a replacement since it shouldn't be doing those problem in the first place since it's new.