The Personal.xlsb worksheet is used, most often, to contain macros that you want available whenever you are using Excel. Normally the worksheet is hidden, unless it has been specifically unhidden and then saved.
To solve the problem, just start Excel and when the Personal.xlsb file is visible, display the View tab of the ribbon and click Hide in the Window group. The worksheet goes away, and you should immediately exit Excel. (If you are asked if you want to save your changes, say YES.)
The next time you start Excel, you should no longer see Personal.xlsb because it is hidden. Instead you should see a regular blank worksheet, exactly as you expect.