Not to sound like a jerk but throw it out if it is melting batteries. I wouldn't want that anywhere near my face even if they said it was fixed. If it is melting them indeed you are one lucky person something worse didn't happen. What kind of batteries were you using, could it be bad batteries?
It probably be cheaper or the same price to just buy a new one you don't have to worry about.
Go on Smok website and see what they say if they get back to you which they tend not to do or it takes forever from what I have seen, no experience with there customer service myself.