Why is my eye suddenly puffy?

I recently just woke and got up to use the restroom, but looking at myself through the mirror I saw that my eyelid was bloated. It doesn’t hurt, nor is my vision blurry. I wondered if it was some sort of irritation- but again it isn’t painful. I do sleep on the same side as the eye that’s currently like this, but knowing the kind of person I am- I’m getting worried that this is something more serious then it looks to be. Can somebody give me tips on what to do to make this go down, or maybe something that caused this to happen?