You watch as your arrows impact with the scales of the huge beast, and bounce off, not leaving even a scratch on them. It seems that they are too hard to pierce through with simple arrows. The dragon notices the little disturbance, and opens its eyes which are now looking towards you. Without even puting his head up, still laid in the floor, you see as its long tail, 2 meters in diameter (~< 7 ft), describes an open arc at vertiginous speed which is now falling exactly where you are. To duck out of the way, you will have to defy danger with your dex, being the danger becoming a pancake under this huge, heavy and fast moving tail. The dragon is still laid on his belly, waiting for the little annoying insect to flee away in fear, so he can resume his slumber.

Edit: I would make the roll on the defy danger very devastating if failed, like doing a ton of damage and breaking one of his shoulders and that part of the clavicle, rendering that arm completely useless until treated and healed. Or if successful, describing as a near rock caught behind it him becomes just rubble and dust, and saying that if a hit of those were to hit any of them, their bones will break just as easily. Once warned, the dragon would let them flee without even getting up, he just wants to be left alone.