Trackpad is stiff after dropping liquid on it

A couple of days ago, I dropped a small amount of orange juice on my 13" MacBook Air's (mid-2012) trackpad—maybe just enough to cover 1/4 of the trackpad.

I immediately turned it off, dried the liquid with paper towels, and turned the computer upside down, covering the trackpad with paper towels.

I let it stand for a couple hours before turning it back on. Everything's fine, but the trackpad button is kind of stiff, kind of hard to click. It just doesn't do that "click" sound anymore, and it doesn't go as deep into the body as it used to. It works flawlessly otherwise.

Today, it started working as it used to, but it's now stiff again.

Thing is, I still have warranty on it. Is it possible that the liquid hasn't gotten into contact with the LSIs? Is there another way for Apple to know if it's liquid damage other than the LSIs? Should I just try opening the computer myself or should I go to the Apple Store?

Thanks.