Will my broken nose stop changing shape? How long will it take to heal? Can I use arnica?

Thanks for the question. I recommend you to send your photos to us to give you the advice you need and want or to have a personal evaluation. Kind regards 

Arnica is a homeopathic remedy that addresses bruising - not broken bones.  Trauma to the nose can cause extensive damage and changes. Best to seek an experienced Board Certified PS for in person exam. You may be a candidate for corrective Rhinoplasty that potentially would give you your best looking nose.

In reverse order, yes...you can take arnica, but it may not do much for you at this point.  It is used to keep down bruising, but since you are 2 weeks out from trauma, I suspect it will have little to no benefit for you now.  The nose will stop changing shape over the next several weeks, but it is dependent on too many factors to address here.  If it is just swelling after the trauma, then it will be done in the next few weeks, most likely.  If there is underlying cartilage, or worse, broken and displaced fractures of the bone, the problem may continue longer and leave you with new problems, such as breathing (air flow) issues in the nose.  I recommend seeing a Board Certified Plastic Surgeon for a complete evaluation.

After trauma to the nose, it's always best to seek out a thorough internal and external examination of the nose to document the extent of the fracture both internally and externally on the nose.  Trauma to the nose can cause a displaced or a non-displaced nasal fracture, dislocation of the upper lateral cartilages off the nasal bones, and a fracture of the nasal septum also known as a Deviated septum. A rhinoplasty can accomplish straightening the nose to make it look more symmetrical, while a septoplasty can improve breathing if needed.

The nose can stay swollen and change in shape for up to 12 months after a fracture. The bones often set in 6 weeks however the cartilaginous deformity can worsen with time due to the inherent pulling forces from the broken bones.  You should see a facial plastic surgeon for further assessment, as you will likely need surgery to fix your problem.  Arnica only reduces swelling.  Hope this is helpful.