Better than a cacking noise
.
If there's no play in the headset the only thing I can think of is possibly over tightening of the bolts, had this once when I was a bit ham-fisted with an allen key. Probably not doing any real harm but a) not a nice noise to hear when you ride, and b) better safe than sorry, so probably best to drop it in a (decent) shop and ask them to give it a quick shufty. They can probably sort whatever the problem is in a couple of minutes. Other than that try loosening the bolts a bit and then re-tighten, switching between each one all the time to do up evenly, and just avoid really cranking them up at the end.