Crossfire loud bang..

I make a very stupid mistake: on my gpz900r i switched the coil 12volts wire. So after some cranking i had a terrific bang from the exhaust. Is this a thing that damaged my engine?

I doubt very much there is any damage... however, I had an baffle silencer blow out of an old Triumph once when doing a goof like this.

Yeah, gas collects in the baffle then BANG. If you're lucky no damage.
Steve