Did you quit drinking as well?
Serious night sweats (I mean, the whole bed; mattress, all the sheets, the blankets, the pillows are soaked to the point where you can twist the blanket and water will cascade out) are one of the possible symptoms of HIV...but it doesn't sound like it.
But, quitting is another possible cause. When I was in the middle of drying out, for a good 3 or 4 days it was hard to sleep, I'd sweat a lot at night, etc.
Give it a week. If it's still really really bad, I'd check with a doc. Maybe he can put you on some meds that'll ease the symptoms.
If you notice a slight tremor in your hands and whatnot..that's another withdrawal symptom. Give it a week, you should be GTG...a month after you've quit you'll wonder why on earth you smoked in the first place. 6 months later you'll find yourself not wanting to eat at places that have a smoking section. Just wait, it gets fun