First say Bismillah 3 times and after that say 7 times:

أَعُوْذُ بِعِزَّةِ اللَّهِ وَقُدْرَتَهٖ مِنْ شَرِّ مَا أَجِدُ مِنْ وَجَعِي هٰذَا

A`udhu bi-`izzatillahi wa qudratihi min sharri ma ajidu min waja`i hadhaa.

I seek refuge in Allah’s might and power from the evil of this pain I feel.

Reference: Sahih. Tirmidhi: 3588