Select the Rectangle tool and draw a rectangle where the nose ought to be:
Use the Push/Pull tool to pull the rectangle out into a rectangular prism:
Select the Line tool and draw lines to define the shape of the nose:
Use the Push/Pull tool to push the part that's going to be trimmed off the nose away:
To draw a line, just select a point on an rectangle edge element, then select another point on another edge element. A line is drawn between the two selected points. You can also simply left-mouse-click on any face to start a line.
When the push operation reaches the far side of the nose and "thickness" becomes zero, SketchUp assumes you want the area removed (it gets deleted automatically):
Repeat as necessary to trim other areas, in this case the bottom part of the nose:
All kinds of shapes are possible to differentiate characters, it's a matter of taste.
The last example above uses arcs instead of straight lines to define the nose shape before trimming.
Cosmetic Tip - Getting Rid Of Unwanted LinesI might as well mention this here as anywhere else.
The nose's geometry lines kinda draw attention the fact it's made of geometry. These lines can be easily hidden by right-clicking on them and selecting Soften from the pop-up menu:
To achieve this cleaner look below I just right-clicked on each line around the nose and selected Soften. It's kinda boring but worth the effort.
SAVE THE MODEL.
Next step: Mouths
Intro | Heads | Eyes | Eyebrows | Copying Eyes & Eyebrows | Noses | Mouths | Hair & Ears