Q. Can I have multi-level nesting in Azure?
A. Yes. Providing you are running a SKU that supports nesting (e.g. v3 of D or E series) then once inside the first level VM once you have installed Hyper-V at that point simply follow the normal processes for Hyper-V to enable nesting within its VMs, for example make sure it is using static memory and have enabled the virtulization extensions on the CPU, e.g.
Set-VMProcessor -VMName <VMName> -ExposeVirtualizationExtensions $true