water

Not sure exactly what you are asking assistance for. If it has moisture under the protective case you have it in, I would think that you want to remove the case to get rid of this moisture before it works itself into the phone.

If this is not what you are referring to, you will need to provide a bit more detail on what exactly the issue is. What you have tried doing to resolve it yourself, and finally, what assistance are you looking from here.

And rice grains are just the right size to block up the lightning connector.

Yes as Lobsterghost1 says, the phone is probably destroyed. If you have a son with special needs you might consider buying AppleCare+ to protect against this kind of expense after accidental damage.

Unfortunately, Rice is an old wife's tail and cannot get moisture out of an iPhone. There really is no way to dry out electronics once they get moisture inside.

If the phone is damaged from water, it will have to be replaced. A liquid damaged phone cannot be repaired, nor will Apple attempt to.

Schedule an appointment at your Apple Store Genius Bar and if it is determined the phone has suffered liquid damage, you'll either be offered the opportunity to buy an Out of Warranty replacement for about 60% of the cost of the phone when new, or buy a brand new iPhone.