No one can draw perfectly. That is the reason, it is important to be able to change the drawing by editing the line. Inkscape allows editing by using the second tool on the left toolbar, the Edit Path by Node. See the example beow. The pencil tool was used to create the line and then it was edited by moving the nodes.
A simple lesson to use line editing is the creation of Blobs. Blobs are imaginary creatures that must start with a line and can not look like any real animal or TV character. They have to be unique and completely imaginary.
Here are the steps in making a simple blob.
1. Start with the Pencil tool and draw a line, closing it to make an arbitary shape. Click on the Edit Paths by Node tool, to find all the nodes. Move the nodes till the blob shape is created. See below the way the original shape has been changed by moving the nodes.
2. Select the blob and pick a color
3. Draw the eyes. It is important to draw large outside the blob, and then add them to the blob. A simple example of eyes, is 3 circles. and then select them all and click on Group (Control G). See below for the 4 steps involved, creating 3 circles – white, black, white and then grouping them.
4. Reduce the size of the eye, duplicate (Control D) and move them on to the blob. Use the Pencil tool again to draw a smile. This is a very thin line and can be made thicker. Click on the smile and open the Fill-Stroke window, tab Stroke Style and change the value to a larger number (e.g. 5) to make the smile better. See below.