Hi
my ds (10) was diagnosed with Tourette's at 4 - not true that it can't be diagnosed earlier - however kids have to have both vocal and motor tics for more than a year in order to be diagnosed. Vocal tics can be anything from sniffing, coughing, grunting etc to full-blown coprolalia (uncontrollable swearing) although that happens in only a minority of severe cases. Motor tics can be things like blinking, grimacing, head jerking or sudden arm movements
If kids just have vocal OR motor tics then they will only be diagnosed with a "tic disorder" - if the tics are present for less than a year then it will be considered a "transient tic disorder". Loads and loads of kids have transient tic disorders - it's very common especially around junior school age and nothing to worry about unless it's affecting the child's quality of life. My dd had vocal tics for a while between 2.5 and 3.5 but they never bothered her, and they've now disappeared.
Tics are involuntary movements - they're not done to get attention, to annoy people or to wind anyone up. Children may be completely unaware that they're doing them, or be horribly self-conscious and worried that everyone's staring. However, if their attention is brought to the tic it will make it worse - it's like someone telling you that you have a really itcy mosquito bite but you absolutely mustn't scratch it - the urge just becomes uncontrollable. Most kids can hold tics in for a while once they realise what's happening, but they will have to come out eventually and the longer they've been suppressed, the greater the flurry of tics once they feel safe enough to 'let go'.
For most kids with TS, the tics themselves really aren't a big deal - it's the stuff like OCD or ADHD which often go hand in hand with TS that cause them problems. There does seem to be a genetic link as the condition often runs in families - my dad has it, my sister sniffed and blinked constantly as a child - but as it's a spectrum disorder the trait could manifest itself as anything from a simple blinking tic which people probably wouldn't ever notice to massive full-body jerks and shouting out swear words. The vast majority of cases though are towards the milder end, so even if he does have TS it almost certainly isn't a big problem.
Personally I wouldn't take him to the GP just yet unless there's anything else that's causing you concern. But it might be an idea to keep an eye on it, and if it continues or gets worse get it checked out.
hope theis helps a bit - if you've got any more questions feel free to ask