Sorry to hear about your speaker
.
All though this doesn't help you with fixing your tweeter. A Hi Fi dealer told me when i was buying my B & W 684s that if the dome was depressed, it didn't matter because in 95 % of the cases it won't make any difference to the sound reproduction.
In the case that it doesn't hurt the sound, i think i'd just put the dust covers on and try and forget about it, as i wouldn't want to risk making it worse.
B & W 684 theater, Onkyo 605, NAIM CD 5i, Samsung LE32R, PS3, Qed Silver anniversary XT and Chord Silver HDMI