How to fix the nose in this portrait of soft oil pastels?
To me the proportions look right. I think your problem is the contrast in color between the tip of the nose and the skin above the upper lip.

In your reference picture there is a very soft and gradual blend from nose to upper lip. The lightest color is on the very tip of the nose, where most of the light is reflected.  The parts of the nose that physically point downwards lie in a soft shadow. At the same time the nose casts a soft shadow onto the skin below. Both parts have a very similar color. It's impossible to see exactly where the nose ends and the skin above the lip starts. 

In your painting you painted the shadow below the nose, but all parts of the nose are very bright. That creates a sharp contrast and your eye is drawn to that specific point. Your brain cannot stop analyzing this point because of the sharp edges.

If you darken the underside of the nose, this contrast dissappears and your eyes are drawn to the brightest spot - which is now the eyes. The human brain fills in the information that the eyes don't see clearly and suddenly the nose has exactly the length the observer likes best. 

The same effect can be observed in the famous Mona Lisa. All the contours are so soft and blended that each observer sees the image a little different. If you look at her eyes, you cannot see the lips clearly and your brain automatically fills in the missing information with "she's smiling". If you look at her lips, you suddenly realize that she isn't actually smiling, there's just a soft shadow pointing upwards where the corners of her mouth would be if the was smiling.