Throbbing Bones

The caster speaks a word of power over the bone power and blows the dust opon a creature within 10 feet, making a Ranged Spell Attack.  On a hit, the creature's bones physically throb, swelling and shrinking inside, which is both intensely painful and internally damaging.  Each round until the duration ends or the creature makes a Constitution Saving Throw at the beginning of its turn, it suffers 2d12 Bludgeoning damage.  

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the duration of the spell increases by one round for every two slot levels above 4th.