Actually, as a part of the action used to cast this Booming Blade 5E Spell and you should make a melee weapon attack which is against to the creature which is within the spell’s range, or else the spell will fail.
Normally, on a specific hit, the target would suffer the attack’s the normal effects, and also it shall become sheathed in the booming energy but it happens until your next turn starting stage. If the target is willing to move, or does not move before this time, 1d8 thunder damage will immediately be dealt and the spell will end.
We also suggest you to read: fizban’s platinum shield 5e spell
At higher levels:
Actually, in this d&d 5e Booming Blade Spell at the level of 5th, the melee attack would deal an extra 1d8 thunder damage to a specific target, and the damage the target will take for moving increases to 2d8. In fact, the damage rolls at 11 and 17 levels would both be increased by 1d8.
Attributes of the Booming Blade
|Casting Time||1 Action|
|The Range||5 feet|
|Components||V, M (a weapon)|
|Classes||Wizard, Warlock, Sorcerer|