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I read this at least twenty years ago, but have no idea how old the book/story was.
Set in some indeterminate point in the future, typical have & have nots style. The youth battle each other using various weapons but guns are banned for not being 'sporting' (not sure if all projectile weapons treated the same).
The protagonist uses nunchucks and is a loner.
Somehow he gets involved with some science group who are investigating weird growths somewhere. He gets injured during this but has something in his pores that 'crawl' out and heals wounds but somebody doesn't understand them and keeps picking them off.
The only thing I recall is that he actually has a shotgun shell embedded in one end of the nunchucks so this could be used as gun if necessary.