Hi,  New to this site and desperate for help.  I  have a great dog.   he was adopted at 4  months old from, I  think, a  good  environment.   he is very spoiled  by me and my teenage kids.   he gets and is used to a lot of physical affection  by us  and all of my kids friends.   the worst part of his life is that he is home a lot  alone during the day  but is not overly destructive unless something is left out abd looks/ smells appealing to him.   he goes to the dog park and has a best dog friend that visits a  couple of times a week  so I would consider him very well socialized with people and dogs.
a  couple of times he's been in the car  with me and somebody reach into pet him  through the open window.   he did not like this and nipped them and even knew one of them.  I  firmly told him no and assumed it was just something with the car.   he also did this once in public when  we were at an outside restaurant and he had a leash on that has gotten tangled under a chair.   when a  stranger  reached to pet him,  he nipped.  
now,  all of the sudden,  he is doing this to everyone who tries to pet him outside of our house.   hasn't drawn blood and doesn't growl or show any other aggression.   just doesn't seem  to want strangers to pet him.  
I  dont want to  stop taking him places with me,  is there anyway to keep this  under control?
when a side note he's never really seem to like his head  pet much,  even by me,  but at least he just paws my hand away and rolls over for a belly rub.
please help as I dont want to take any chances.

There is a distinct difference between biting and husky nipping. Huskies do a lot of teeth on skin play and if you haven't taught him that this isn't acceptable, this may be what he's doing, trying to get people to play with him. You need to teach him that this is unacceptable.

oops... forgot to add some important information. I mentioned we got him at 4 months. that was a year and a half ago. he is now 20 months old ( almost 2 years). so I really dont think he was abused and certainly is not now our for the last year and a half almost. my kids are older teenagers and adore him. this is just a new behavior. I almost feel like it is because he had never liked his head pet and is now so comfortable and confident that he is comfortable telling people "no". I just don't know how to properly correct it? he is not drawing blood and is happy and wagging his tail otherwise.

You could try as best as you can to positivley introdue a muzzle for those situations so he understands you don't want his mouth on people.

I had this issue with my husky when he was younger. He's not aggressive and has never bitten anyone, but because "he looks life a wolf" (stupid people,) he's big and scary. I taught him to touch my hand and then when I introduced him to strangers, I would tell them to put their hand out and ask him to touch, he would- and then immediately look to me for his treat. I rewarded him A LOT and kept the sessions really short, if people ignored me asking them to back off when he got overwhelmed- I'd just walk away. I don't care if they thought I was rude, my dogs well being is more important than what some stranger thinks of me. Anyways, he is now a certified therapy dog! I was once at the cross roads you're standing at.. you just have to decide; do you want to address the problem head on? Or do you want to take precautions and avoid those situations? Whichever way you go is fine, just trust yourself, your decision, and your dog