Disclaimer: You cannot add more brush strokes to your drawing, nor use the eraser tool once you have clicked the ‘Finish drawing’ button.
There are, however, other things you can change in your drawing and the design as a whole.
You can move, resize, and delete your drawing.
You can also change things like the color, brightness, contrast, and vibrance of the design as a whole.
Additionally, you can add effects and filters to a finished drawing.