Welcome to the (disappointing) world of autoflowers, which flower once the reach a certain age, not size.
Once these pistils appear, flowering will start in earnest in about 2 weeks time.
Unfortunately, your plants will be rather limited in size and therefore yields will also be limited.
There is nothing you can do to stop this flowering process once it begins and this is why the first vegetive weeks of life with autoflowers are so vital to get some size to them, otherwise you end up in the situation that you are in, namely dwarf plants flowering.
They may still double in size, but even then your yields are not going to be huge.
I gave up growing autoflowers for good due to these sort of uncontrolable outcomes and will never grow autos again.
In future, stick to photoperiod feminized plants, you can control when they flower and then get any size of yield you would like.
Autos are really best left to hydro, big lights and experienced growers, feminized photoperiod plants are far more forgiving and far better suited to new growers in my opinion.
You can also save a lot of money, as photoperiod plants require less hours of lighting to produce a crop, rather than the months of 18 hours per day of light that autos need.
With photoperiod plants you need a short veg period at 18 hours then a couple of months at 12/12, meaning your electricity bills will be much reduced when compared to growing autoflowers.
Using a fairly typical 12 week cycle as an example........
Autos = 12 weeks at 18 hours = 1512 hours of lights on time.
Photo fems = 4 weeks at 18 hours = 504 hours, plus 8 weeks at 12 hours for a total of 1176 hours of lights on time.
Therefore, over 12 weeks you save 336 hours of "lights on time" by growing photoperiod plants.
I know which electricity bill I would prefer and whose "carbon footprint" is smaller!
Hope this helps, Organoman.