Answer: As long as you have kept the container raised up off the ground an inch or so to allow for air circulation and drainage under the plant, there shouldn't really be anything in the soil. I would suggest washing it with a spray of water from the garden hose twice a week, and then prior to bringing it indoors perhaps a spray with commercially formulated insecticidal soap being sure to contact all sides of the foliage and stems. Then keep a close eye on it in case any whiteflies, aphids or spidermites might have hitchhiked in despite your best efforts.
This is a tropical plant so do not allow it to get colder than about 55 degrees if you want to try to keep it blooming indoors this winter. Bring it into the brightest possible location, provide good air circulation and ample humidity. Take care not to overwater as it may use less than it did when outdoors in the wind and sun. As growth slows you should also cut back proportionately on the fertilizer until spring. It may lose some leaves due to being moved, this is fairly typical.
I would not repot it now as it will begin to slow its growth as the days shorten. I would wait until late winter, early spring when its next growth spurt starts. That would also be the time to do any needed pruning. Generally since this plant is such a sun lover it does better if you can summer it outside, but if you have a truly bright indoor location you can try keeping it there year round and see if it is able to bloom there.
Good luck with your hibiscus!
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