Changing workspace in visualstudio after renaming computer name

run in the Developer Command Prompt for Visual Studio
to get workspaces on your computer and getting collection name 

tf workspaces

result will be like 

Workspace     Owner      Computer Comment
------------- ---------- -------- ---------------
DEV2           Your Name COMPUTERNAME

DEV2           Your Name COMPUTERNAME

after that run following command:

tf workspaces /updateComputerName:MyOldComputerName 
/s:"http://MyServer:8080/tfs/MyCollection"

https://www.visualstudio.com/docs/tfvc/workspaces-command