He's right about topping creating more colas. If you have 3 ft of grow height, personally I would've left it to grow a few more nodes before topping. There are some crazy techniques out there, though. Mainlining comes to mind, and even then it's suggested that you wait until the plant has 5 or 6 nodes before making the first cut.
If everything else in your grow environment is good (temps, humidity, light, soil, feed, etc) your plant will be fine.