Is the small size(4mm) of chin implant for me? (photos)

In just looking at your after surgery side profile, there is room for more chin augmentation without looking too big. It would also be helpful to see full face pictures with one before surgery as well.

Sizes of chin implant very amongst manufacturer's and amongst  Shapes and sizes. The size of the implant is  decided at the time of examination and consultation with your surgeon, when they are examining the chin in a three-dimensional fashion, and discuss your goals of what you're trying to accomplish. In our practice, the far majority of patients undergoing chin implants are small and medium size.

The photo you posted above, in my opinion, would benefit from a small to medium chin implant.  It would be nice to see a full face for better evaluation.  If you place your finger rom your lips straight down, your chin should almost touch your finger (men touch; women almost touch)  Yours is behind.