IPhone USB port not recognising?

I just dropped my iPhone in a mug of tea. (It's a big enough mug for it to go through.) Not much tea went onto my iPhone and I wiped it off quickly. My iPhone is still working. However, a while later I got a message saying 'Charging is not supported with this accessory.' I thought nothing of it until i went on the music app and it turns out it believes an accessory is plugged in, like a speakerbox type one. The same message now appears as my background before becoming unlocked.

It doesn't look like there's any damage to the USB area. What should I try to do to solve the problem? Would it be ok to plug any actual accessories in and try to charge etc?

It seems that the USB connector is damaged.
First of all you should try to change the USB cable to see if the problem persists. If it does you should try the factory reset function, because it might be a problem with your OS. I say that it might be a problem with the OS, because lots of users who jailbroken their devices are complaining for lots of bugs lately. This happens because they really don't know how to do a jailbreak procedure. If you want to do a proper jailbreak, my advice is to go to http://www.deviceseeker.com and search for jailbreak tutorials. Attention - before you delete all your iPhone data, make sure you back up all your files.