some doctors inject Botox off-label to decrease the effect of the tip of the nose lowering during smiling. Usually only 1 or 2 units are needed, but if the surrounding tissue is affected than the upper lip might drop. if it is the shape of the nose, then possibly, filler injected conservatively may help.
The information provided in Dr. Shelton's answer is for educational purposes only and is not intended to constitute medical advice. The information provided should not be relied upon as a substitute for consultations with a qualified health professional who may be familiar with your individual medical needs.
Web reference: http://www.thenyac.com/botox/index.html