Depends on the slots you used: Warlock slots are always at max level you could cast as a warlock. Your sorcerer spells are differnt. But you are allowed to cast sorcerer spells with warlock slots and vice versa. You may even use warlock slots to fuel sorcery points IIRC. Does not matter when you dip. As vasrer your cantrips go up with total level. So your baseline damage increases fast enough. Especially with warlock's agonizing blast.
