It all depends on how much "jerk" forward you get, It could be a clutch adjustment problem, or if you replaced the oil after you dropped and repaired it, it could be the new "thicker" oil that tends to do this, or if the weather is very cold.
Does it still do it when the oil has heated up a bit???
A lot of bikes have got a little bit of "jerking" forward if it was in neutral and you shift into first.
If this is only slightly, it should not be something serious. Like the previous guys said, try first to determine if the clutch do release completely when pulled in.
"Too much power is just enough!"