First backup just in case. Try to delete the Plugin from your directory. Also rightclick and open YourProject.uproject with a Text Editor and remove it from the Modules/Plugins. Rightclick your Project file again and choose Generate Visual Studio Project Files. Open your Solution and Rightclick your Project and choose Rebuild. Try to Open your Project and See if it works.
If you really dont use it anywhere it should clean all things up. Also if you ever deleted files directly from VS they still exist in your Source directory you maybe want to look into it just in case.
Hope this Solves the Problem for you