Dry Socket is something that a small percentage of people having teeth extracted will develop. Smokers develop it at a slightly higher percentage. Smoking does not always cause dry socket just as abstaining from smoking does not ensure that you will not get it. Dry Socket develops when the bloot clot in place after the extraction comes out. This exposures bone/nerves to the air and to bacteria from food, etc. You can get Dry Socket from the suction related to smoking or using a straw, or from risnsing you mouth excessively, grinding your teeth at night, brushing the extraction site too soon, etc. Basically anything that will dislodge the clot can cause dry socket. Dry sockets occurr almost exclusively on bottom molars and bottom wisdom teeth. Generally it develops 4-5 days after the extraction.
If you get dry socket and are in bad pain, pain killers will not touch the pain. The only thing that works is Oil of Clove or the active ingredient which is called Eugenol. The dentist/surgeon will pack the hole with gauze soaked in this and it will get rid of the pain instantly. The stuff is horribly disgusting, but when you have a dry socket, you won't care one bit about the taste. If it's over a weekend, or you just can't go back to the dentist right away, you can buy kits containing eugenol from the drug store. Soak a smallish peice of cotton in the eugenol and stuff it in the hole. This will get rid of the pain until you can see a dentist.
Unfortunately I've had far too much experience with dry socket in my lifetime. I get it due to grinding/bruxing my teeth during the night. I smoke also, but my dentist told me that unless I felt the clot dislodge while I was smoking, it wasn't the smoking that did it, and that tooth grinding is the most common cause. Of course, most dentists don't tell you all of this because most of them are passionate anti-smoking fanatics, so they always try to get you to totally abstain after extraction in the hopes that you will quit smoking.