We both came to the conclusion that "Feel the Pain" is about drinking. The cork at the begining symbolizes the drink of choice being opened (wine, champange, ext.) and the main lyrics (I feel the pain of everyone, then I feel nothing) tells how before he drinks, he feels the pain, but after he drinks, he feels nothing.
But I seem to remember an interveiw with J where he said the song was about the time he broke his leg.
I guess the drink could be replaced with morphine or some other pain killer?