Take the diagonal out and leave the tube open for the night... and maybe most of the next day to let the air get into it. Don't try and heat the tube with a hairdryer, that'll only make matters worse as it could drive the moisture into nooks and crannies you don't want or need it to get into. Let it evaporate naturally.
Just leave it open and it will gradually disappear, could take a while but it will go, don't heat it or blow dry it, all will be good, it is not an uncommon thing to happen to scopes.
