While it may be a cute capture of your child, I don't believe it constitutes a portrait in that it is not a planned, posed image. As mentioned, the angle and background take away greatly, as does the exposure.
If you want to do a nice child portrait, find a nice plain background, free of distractions, preferably with lots of sunlight (I'm assuming your equipment is limited) and place the child so that he is well in front of the background and the sunlight is illuminating the side of his face. Next find a reflector, white sheet, piece of white foam-core or posterboard, etc and place it on the side opposite the window and out of camera view. Now, get down to his eye level and with your pop-up flash up (unless you have a removable flash) and a diffuser over it (small piece of tupperware, piece of tissue-paper etc), start shooting.
I would go with aperture-priority mode (A / Av) and use flash exposure compensation (refer to your manual if you're not familiar with this) to reduce the flash output and vary your aperture until you get the largest aperture you can (smallest f #) and still have a decent shutter-speed. Set your camera's rear LCD to display blown highlights (commonly called the 'blinkies') and adjust your flash output until you have none or almost no blown highlights and a nice exposure. Your histogram should look somewhat like a Bell curve.