I'd sniff the bottle to see if it smells off (from the usual... I know Prime always smells like rotten eggs, lol) and maybe pour a little out (or suck it up in a syringe or something) into a clear container to see if it's changed color, if there are any particulates that formed, if it's bubbling or any other sign of a chemical reaction. If not, it's almost certainly fine. If it is reacted, I'd toss it out and get a new bottle, unfortunately, but I kind of doubt anything happened.
I think the Prime could have bound and probably did bind the heavy metals and chlorine present in Flourish, but the amount you added was so negligible compared to the size of the bottle that I don't think it matters very much.