It's quite interesting trying to figure out what was going on at the moment you took this. From his pose (btw is he your brother? there seems to be a resemblance to your selfportrait) I get a vague sense of forward motion, but I can't tell if that motion was a) frozen by the camera, b) he was just in the moment of halting, or c) he was about to start moving. As if that were not enough, I can't figure out the expression either. Looks like something between startled, hurt (not by having his picture taken, more like from having fallen from a bike), annoyed? Whatever it is, there's definitely a connection to you. Your presence is felt in the image, and I don't mean by the sole fact that the photo exists. All in all, quite a lot to think about.
The technical aspect I find of interest as well. Colour images generally tend to bore me. Polaroid film seems to do weird things to colours, it gives them a completely different mood. Or perhaps it would suffice to say that it gives them a mood, period. Gotta try this one day.
I am digging the emotion you captured on this kid's face. The colors, slight blurriness, and the darkness of the image help the viewer form a sense of thic child's personality.