Hi, yes as said by blitzteh you have many notifications. Please try to open them and see if it disappears.
If still the dot is there, we suggest you to perform wipe cache partition. Below are the steps to perform clear cache partition.
1.Turn off the unit.
2.Press and hold the volume up button and press and hold the on/off button. When the Android logo is displayed, release all keys ("Installing system update" is displayed before displaying the Android system recovery menu options).
3.Press the volume down key repeatedly to highlight "wipe cache partition".
4.Press the Power key to select. Press the Volume Down button to highlight "Yes" and press the Power button to select. When the wiping of the cache partition is completed, "Reboot System Now" is highlighted.
