Mine had the same problem. The aperture was sticking either fully open, or sometimes not quite fully open, and consequently most shots were over-exposed, unless, of course, the shot was going to be on a wide aperture anyway.
It was sent to Fuji, and they replaced the lens without any fuss. The work was done under their "Platinum Service" (as it's called in the UK, at least), and this provides a rapid turn-around. The camera was returned to me within six days, inclusive of a weekend.
There's no point in delaying the inevitable - I tried to "give it a few days" in the vain (and ridiculously irrational) hope that it MIGHT just correct itself, but of course, it didn't.
I would advise that you just get it repaired, and get back to normality as soon as possible.
Good luck.