Below are the steps, which you can follow to get out of this situation.
1. First, download nuget.exe file from online source in order to perform source update on the nuget.config file.
2. Then, search for the nuget.config in your local environment –> open it with text editor –> search for the tag <packageSources> and get the key value for your Artifactory name.
3. Next, after replacing <Key> with the Artifactory name (retrieved from the tag <packageSources>) and providing user id and password you will need to run the command below:
nuget sources update -Name “<Key>” -User <username> -Pass <password>