My sony ericson phone K10i does not start?(9730715254)?

I have a sony ericson phone (K10I Cyber shot)..i was on a call for 5 minutes.After some time when i picked my phone to make another call. the phone was hot, i immidaitly removed the battery and noticed it had swollen, after some when the phone was normal i tried to insert the same battery but it did not start.. so i bought a new battery but my phone does not start.. PlZ help