Hello dear
Although the pic is not in right angulation, This is not your bone.
It's recession of your gum.
As you have a habit of gutkha , you developed from it.
Next Steps
You may go for a full mouth oral prophylaxis ( scalling)
.And stop chewing Gutkha.
Health Tips
As you mentioned that all reports are normal, you don't have to worry .But if it worsens go to a dentist and check it up .
don't worry