There is no such thing as social smoking. You're either a smoker, or you're not. Of course, people smoke in varying degrees, but your smoking is detrimental regardless (although it may not seem so atm).
My smoking started from a party, then it grew into regular smoking, which is what a lot of 'social smokers' run the risk of. I used to smoke a lot, but I've quit for coming up to 2 months now.
The social smoking will accumulate, and you won't really notice any health changes until your breathing becomes a bit dodgier, you seem to get ill (colds etc) more often that you used to, and if you run for a bit you will probably find you will be out of breath quicker.
Tbh, dabbling in it won't really impact on your health that much, but you tell yourself that you won't smoke regularly, and you seem to slip into it gradually.