Go into your workspace, and move your project source code folder to another area outside of your workspace (like the desktop). Make sure the project is deleted in eclipse, then create a new project from source from that directory.
Another thing you could do is try creating a project of a different name (from the first project’s source), so that the workspace will contain the new project as a functional project. Then, go into your workspace directory and absolutely delete the folder that contained the original project, or move it. Try loading the project from source again, this time using the second project, by naming it with the correct name. Or, you could try refactoring the second project back to the first’s name.