Level
4th
Casting Time
1 Action
Range/Area
120 ft
(20 ft )
Components
V, S, M *
Duration
Instantaneous
School
Evocation
Attack/Save
DEX Save
Damage/Effect
Fire (...)
You manipulate the tiny flecks of matter in the air over a point you choose within range, causing an intense flash of pressure and flame. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 3d8 fire damage and 3d8 force damage on a failed save, or half as much damage on a successful one. Any target that fails the saving throw by 5 or more is blinded until the end of your next turn.
Objects not being worn or carried are thrown 10 feet away from the explosion.
At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the damage (both fire and force) increases by 1d8 for every other slot level above 4th.
* - (A pinch of bat guano and coal dust)
Let me know what could be improved while still being balanced!
Since pressure is part of the explosion and objects are pushed outward, you might want to consider switching from Force damage to Thunder damage.
You can see similar effects on Thunderwave and Destructive Wave.
Other than that it's ok I think.