Try this...after a good ride start it in gear. Does it still pull forward the same amount when the engine is warm? If not it's the oil that hasn't yet thinned out and the overall clutch contraction due to there not being much heat in a cold bike. Heat it up and it loosens up. My brand new KTM has done this from day one.
If after a good heat up it doesn't get better then it's clutch wear. See, clutches as they get old or are abused actually lose the ability to release the gearbox from drive system. This is dangerous so get it replaced today!
Clutch replacement is pretty easy with the right tools or a mechanic can do it in less than 2 hours so don't worry if it's worn out.