I made a fundamental photography error and I need help/advice to get me out of the problem.

I took a photo at a meeting, but there was a mirror which I did not see, at the end of the room. The photo shows the flash from the camera in the mirror - it's obviously very bright.

I'm new to digitally fiddling with photos so I would like advice on how I can remove or reduce the effect of the flash in the (rather large) mirror.

I can't crop the mirror out of the photo. I could try and clone stamp the mirror with some other area so that it looks like a reflection of the wall paper or something. Is there a clever function in photoshop that can cope with this? Can I remove the flash, reduce the brightness of the flash but not the rest of the room, make it more diffuse???

Any suggestions would be great. Thanks in advance, psyberyeti