Home on on iPhone not working?

I dropped my iphone in a little bot of cold hot coco around 2 days ago. At first it was fine, but then the home on only selectively worked. I left it off and face down all night and the home on started working again. Then later on in the day, it started doing like phantom presses, where it was like there was some internalized pressure on the on so whenever I was in the middle of texting or whatever, it would keep going to the home, search, or recent calls screen. The next day, the home on was working again during the day, but now it won't work at all. I can feel the on press down, but it's completely unresponsive. I tried restoring it and the button doesn't work, then I tried to clean it and still nothing. Is there anything else I can do before I have to go to the apple store and get it looked at/fixed? Will going to the apple store to do so coast me money?