I have a multiclass PC with 3 levels in warlock/hexblade and 1 level in sorcerer/divine soul.
This means I have 2 level 1 sorcerer slots and 2 level 2 warlock slots. I can cast cure wounds because I am a good aligned divine soul sorcerer.
If I cast cure wounds using a level 2 warlock slot, do I heal for 1d8+CHA or 2d8+CHA?
The description for Cure Wounds includes:
At Higher Levels: When you cast this spell using a spell slot of 2nd level or higher, the healing increases by 1d8 for each slot level above 1st.
You are casting the spell at 2nd level, using a 2nd level slot. The fact that you can only cast 1st level sorcerer spells is irrelevent.
Therefore, the spell will heal 2d8+CHA modifier hit points.
from the Multiclass rules on pg 164 of the PHB:
Pact Magic. If you have both the Spellcasting class feature and the Pact Magic class feature from the warlock class, you can use the spell slots you gain from the Pact Magic feature to cast spells you know or have prepared from classes with the Spellcasting class feature, and you can use the spell slots you gain from the Spellcasting class feature to cast warlock spells you know.
Casting of a higher level Cure Wounds gives you the extra 1d8 per slot:
At Higher Levels: When you cast this spell using a spell slot of 2nd level or higher, the healing increases by 1d8 for each slot level above 1st.
