Possible Clues:

• Possibly Remus's extremely excruciating back pain
• Double the force of gravity ending in collapse, bringing sudden pain
• Pang (of conscience?)
• Sudden, sharp pain
• Leyton Orient winger's internal darting pain
• Sharp pain (of conscience?)
• One of the pair will start to have it in pain
• A small stab of pain
• Bit of regret
• Slight pang