How can I get rid of this weird dent when I smile? (photos)

This area is a very sensitive area and must be treated in that manner. This indentation or dimpled area should not be filled as that can cause a problematic outcome long term. By looking at the underlying issue which could be a variety of things like loss of volume, laxity, lack of connecting fibers of the muscle within that area. By lifting the cheek area, this will decrease the prominence of the dent within the nasal labial fold. Also with other combination approaches you may find optimal results by simply analyzing the underlying imperfection. Please seek a highly skilled cosmetic surgeon who specializes in combination treatments and facial injections related to sensitive areas that are possible to be treated meticulously. Best, Dr. Berger

There is a new HA filler that's approved in the US specifically for this problem called Restyle Defyne.  If injected in the area, it will erase these lines.   Try it a few months before the wedding to make sure you like the results.