My children were also very gifted at a young age and I simply encouraged their natural inquisitiveness.
Opportunities for knowledge are abundant with any child.Whatever you are engaged in keep a dialogue going,explaining what you are doing and why.
Be sure to help him understand that everyone makes mistakes and that is O.K.If you have to fake making a mistake yourself to prove your point from time to time ,do so. My children at times could be very quick to point out to their peers when they were making an error.Since they did not have diplomacy down yet,it was sometimes very awkward.
Remember also that he is a child first and a gifted child second.
You may want to have him tested so that when school time arrives he is placed in the most ideal circumstance to further his intellect.
Enjoy! He sounds like a treasure!