VirtualBox - Error

I am trying to run a VirtualBox inside another VirtualBox and I am getting the following error:

 VT-x is not available 
 (VERR_VMX_NO_VMX).

 Result Code: NS_ERROR_FAILURE (0x80004005)
 Component: ConsoleWrap
 Interface: |Console {872da645-4a9b-1727-bee2-5585105b9eed}

My original operating system is macOS, my first VirtualBox is running Kali Linux, and the VirtualBox that I am trying to set up is Kali Linux as well.

If you are on a Mac, you likely have an Intel CPU. VirtualBox does not support nested virtualization for Intel CPUs according to the Oracle docs

Oracle VM VirtualBox supports nested virtualization on host systems that run AMD CPUs