If you have version NuGet.exe version 3.3 or higher, you can clear the entire cache from the command line:
nuget locals <all | http-cache | packages-cache | global-packages> -clear
If your NuGet packages are loaded into the NuGet v2 cache, you can simply create a simple script to remove a specific .nupkg file from the package cache.
del %LocalAppData%\NuGet\Cache\NUnit.2.6.4.nupkg
NuGet v3 , :
rmdir %UserProfile%\.nuget\packages\NUnit\2.6.4 /s