PLEASE do some research/ reading on lipo safety and use... tons of info out there on the net.

As for what happened... you drew WAY to many amps out of the pack...that is why it got hot and swelled... probably discharged it to low as well. The pack IS damaged... it may still work but make no mistake it is damaged.

Lipo's are great when used properly... treat them wrong and BAD...BAD stuff WILL happen... for instance... you could burn your house down kinda BAD