I will never understand why people are so eager to show their permit. Especially when it introduces a firearm into a situation where there wasn't one previously.
The answer legally is 'no'. There is no legal requirement to disclose the presence of a firearm either in your car or on your person during a traffic stop.
This issue is a subjective one. People have their own opinions on how to handle this situation.
One school of thought is to hand your pistol permit over to the police officer with your license and let him ask the questions from there if they choose to so.
Another school of thought is to not offer information that is not needed unless being asked to step out of the car or directly asked about the presence of firearms.
By all means, lying to a police officer about the presence of a firearm is likely to end up with you in legal trouble.
Since there is no legal disclosure requirement, this is a matter that is entirely up to you. You should do what you are comfortable with.