A little more clarity here please.
1) If you mean someone else has a package up that you author and don't want on nuget for some reason, then try first contacting the owner of the package to resolve this and if that doesn't work, please elevate it here. You can also talk them into sharing
ownership with you and/or just assigning the package id over to you.
2) If you mean you have an older version and you want to delete it after you have a newer version available, this is not a recommended scenario for package management. Someone could depend explicitly on a version you have up and if you remove it, you would
break other people's packages. You do that enough and they will find a different library to depend on. :D The world of package management is about having the versions up and available for people to get to over time. Some people are used to removing/hiding
an old version once they've released a newer version, but that doesn't fit well with pkg mgmt and is not recommended at all.
3) If you mean you made a mistake and the package you uploaded needs to be deleted completely, then you
can do it. Don't let too much time pass between the time you release a package and realize it's broken though due to #2.
Keep in mind the general idea behind contributions on nuget is that you should never
delete them in case someone else is using a particular version.