Possible Clues:

• "That's painful!"
• When penny drops from pocket there's a shout of pain
• Bite response
• 'That's gonna leave a marK ...'
• Pained expression?
• Distressful reaction
• Oh, you see hothead to express pain
• "Yipe!" (or an apt title for this puzzle?)
• Reaction to an insect bite?
• Yipe