The song was "Lovey Dovey" and in the song T-ara dances shuffling(according to their management agency Core Contents Medias). Because she dances so tough, the accident happened according to the press.
It seems to be very painful for her because her pictures are spread on the Internet specially many masculine gag sites(ridiculous edited pics). South Korea has insane network bandwidth so anyone can download it in minutes.
In my memory, it's the first time that South Korean main TV station broadcasts female's nipple on air. "화영 인기가요" translated to "Hwayoung The Music Trend" is still the top search word on Korean leading portal site Naver.