I li accidentally gave my 6 year old daughter expired cold medicine which is expired in sep 2017 what should i do now?

Relax: These things are combinations of various antihistamines & decongestants with little effect anyway. The dating is required by the FDA, but out of date does not mean toxic, many remain stable for a year or more after that date. The potency diminishes in some, but not where it matters much. I would be comfortable using it for now, but update your supply if you like to use this stuff.