My kid started reading a couple of months prior to his fourth birthday. By reading, I mean, just reading anything in sight. All I did was read to him, extensively. I don't think we differentiated between sight words, CVC words etc. We did talk a lot about words, in general. He sounded out words he had not seen before, if he had seen the word before, he would just say it. It is much more important that my kid continues to love to read than start disliking reading. I am an outlier, in that, I don't believe in rewards (or punishments) for making a kid read.
The way I look at it, all kids eventually learn how to read. It is kids who truly love reading, have a love for the written/verbal words, that tend to flourish in the later years. My only advice would be to read to him as much as possible, talk about the story, point out interesting facts etc. You will see him pick it up. There are tons of books for that age -- Mo Willems is especially great for that age. Start off with those, you will see his interest and enthusiasm coming back.
