Could he have sore teeth?

My foster dog eats EVERYTHING - he's chewed a fair few things now but I put it down to him being a young terrier and just manage the situation - he has plenty of his own things to chew on and only gets things he shouldn't when I accidentally leave them in the way.

He's eating find and doesn't seem bothered by his teeth, however, I've noticed every now and again (usually if he's been playing with the others) he'll stop and rub the side of his mouth with his paw.

I think he's around 10 months so should have finished teething by now? He has all his adult teeth anyhow... do you think it's worth looking into? I'm not worried, but someone asked me 'what's wrong with him then? Sore teeth?' when I mentioned how much he chewed and I dismissed it, until he started rubbing his mouth...

Ta!