Water damage - home button stuck

Hi guys,

So my iPhone 6 dropped out of my pocket and landed in the toilet. I immediately switched it off and opened it with a repair kit (following an instructional video). I wiped it all down and made sure no water was in there. It's working fine but for one problem; the home button is continuously activating.

It's not stuck pressed in or anything but it's as though my finger is pressed down on it all of the time. When I open an app it immediately goes back to the home screen. When I hold the power button to switch it off it takes a picture.

Does this sound like a motherboard problem or a simple button replacement?

Thanks in advance.