The only option is to attempt to crack it using brute force... The wallet files for MultiBit are encrypted using AES256 encryption. Your best option for brute force attack is probably using gurnec's BTCRecover tool...
It requires that you can use Python and the command line... And you'll also need a fairly good idea of what your password might have been... Or you need to have used fairly simple password.
If you have absolutely no idea what your password was and/or you used a relatively long and/or complex password, chances of successful recovery are pretty much zero
Refer:
https://github.com/gurnec/btcrecover
