Take battery, sim, memory cards out, put in a fan oven at its lowest setting (40-50C) for an hour or two, let it cool and it'll be fine.
Even better if you've got a small Torx driver and can just disassemble it but the above approach works well and for all sorts of things (eg a friend who's daughter's phone took a dunk in a river and was in there for five mins while they found it again.)