Will Botox for my prominent chin reduce its size and give me a softer look? (photo)

Botox relaxed the muscles. It is most likely your chin will be the same size since the only area we treat on the chin is the mentalis muscles and the chin is formed by many muscles and fat pads that will be unaffected by botox. Botox can make your chin look slightly longer, but I do not think it will be significant.

Typically with a projected chin, one would need to consider surgical options for optimal results. Botox in the chin helps with dimpling / wrinkles and not so much reduction in size. If you notice that your chin bobs up and down when you speak, chin injections with botox will reduce this movement when speaking. Looking at the photo you posted however, I think your chin appears to be quite balanced with your lower face, however without seeing a full face profile it is hard to see the true proportions. If you are not interested in surgical options, consider finding an injector who does full facial balancing to reduce the focus of your chin - and balance it proportionally with the rest of your face utilizing dermal fillers.