It is narrated from Sayyiduna Ka'b bin Malik (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When any of you feels pain somewhere, let him place his hand on the spot where he feels the pain, then say seven times: 'A'udhu bi-izzatillahi wa qudratihi ala kulli shay'in min sharri ma ajid' (I seek refuge in the might of Allah and His power over all things from the evil of what I feel)."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16229