Top part of my touchscreen not working since dropping it in a toilet.

A few months ago, I dropped my iPhone in the toilet. It was still powered on when I took it out and there was a red line through the screen. I turned it off within minutes of getting it out of the toilet bowl and then put it in rice for the night to dry it out.

The next day when I took it out, it seemed to be working totally fine but I realized the top left and right corners of the touchscreen no longer work. I'm assuming this is due to some sort of water damage?

I've been living with it up until now and just not using any functionality that involves me selecting something in a top corner (which is relatively avoidable but a lot of apps use these corners for "post" buttons so it's getting frustrating). Everything else about the phone works just as it should.

Any ideas what could be wrong/how to fix it? Is this something I can get fixed in an apple store without spending a ton of money or am I out of luck?