The good news: there was probably no TNT on the fireworks, even from a professional display. Trinitrotolulene (TNT) is not used for any display fireworks that I am aware of. (Building demolitions in Las Vegas could be the exception. )

The solution: wash it a couple of times and hope for the best. You might test positive for nitrates (components in many solid explosives) but you probably won't if you wash it a couple of times. I've handled a lot of fireworks on the 4th/New Years, flown soon afterwards, and never set off the puffer or ETD for nitrates.