Place it right before the moment the hand pulls back, then follow it with a Bruh sound for the stunned reaction and an Emotional Damage sound if the scolding turns into a full roast.
About this sound
This nine-second clip features Dr Nefario speaking the Portuguese phrase 'tira a mão', telling someone to take their hand off. His firm, annoyed delivery makes it feel like a sharp warning from a fed-up scientist, perfect for a playful scolding when someone is touching something they should leave alone.