As you know water and electronics and electricity are not a good mix.
The impurities it the water causes corrosion and provides circuit paths for the electricity which were not in the camera's operating design and could damage the components.
First do not turn on your camera and then you need to remove the battery as soon as possible from the camera to minimize further damage.
Then you need to dis-assemble the rest of the camera and clean all the affected parts using Isopropyl Alcohol 90%+ (available from electronics parts stores) to remove all traces of corrosion and water. Do not use "rubbing alcohol" as in some cases this is only 70% IPA or less, can contain scents and is not as effective. If you do have to use it check the label to verify the amount of IPA
Here is a link that describes the process.
Electronics Water Damage
As always with electronics, especially surface mounted PCBs be gentle when handling and especially when brushing away the corrosion. You do not want to remove any components from the board.
Hopefully after you have done all this the camera might possibly work correctly again.
Here is a link to the ifixit Nikon D3200 Repair guide(s) for your camera.
If this process seems too daunting, take your camera to a reputable, professional camera repair service and ask for a quote for a repair. If you decide to do this, do it sooner than later.