Mine are the same a loud ouch and stop the playing should be enough.

I agree with realspeed almost entirely BUT beware of tapping under the jaw.

I can only speak as an owner of terriers for more than 25 years, but if you do that or tap it on the nose you MAY cause further issues. A terrier will see that as an attack and COULD retaliate next time by becoming more aggressive. I would suggest that should be avoided.

You must be calm with a dog , regardless of your feelings. Loud voices can be seen as excitement and can increase their stress levels.

I think a good alternative is to firstly ignore the dog , particularly eye contact, do not speak to it , even to reprimand it , just push it away ( gently but firmly ) and get on with something else. If the problem persists isolate the dog in a separate room , preferably with no stimulus , dogs do not like isolation. This should only be for a minute or so, then remove the dog , if he continues then return to the room for another minute or maybe two. He will soon get the idea bad behaviour will result in isolation.

Overall we must remember they are dogs and not people and have totally different mind processes to humans, they are not little children.

Agree with Reeventu, we were told that raising a hand to a dog even for a slight "tap" can cause the dog to see any raised hand - even for a pat or stroke - as a potential threat. From a time when dinosaurs weren't just confined to zoos!