I didn't have time to add a little technical addendum to my previous post:

You can certainly play a Bb note against an F# chord because the F# triad contains the note of A#/Bb. But if you play an F# note against a Bb chord - major triad Bb D F natural - it'll sound as though you're pulling out the devil's public hairs. And - unless anyone has a truer version - the lead note in the bar in question is F#.