Arcane Spike

Conjure a barbed spike made of mana and fling it at your foe, dealing 1d4 damage. On hit, the target must make a constitution saving throw. On a failed save, the spike  burrows itself into the enemy and does 1d4 damage per turn until it is successfully removed. On each turn the target can attempt to make a Medicine check to carefully remove the spike and take no extra damage, or another Constitution saving throw to tear the spike out, dealing 1d6 damage to the target.