I don't pinch my begonias at all and they get big beautiful blooms up until frost. The small flowers you are seeing are the female flowers. Pinch them off if you want.

my question Is can you rebloom a reiger begonia. I read that when they stop blooming to cut them back to three Inches and put In a cooler place until they start new growth agian. I also read somewhere to just keep them where they get god light and they will rebloom again. which Is correct? mine Is still giving out a bloom here and there and Is getting quite tall with alot of new leaves. what should I do? thanks