Hmm, burn-in should not happen based on so short a period of displaying something in a particular spot. That would be really unusual - generally it takes hundreds of hours of showing the same thing to do permanent damage.
Unfortunately, there really is no good solution for burn-in. You can make it less visible by running any one of a number of "screen fixer" apps, but basically what they do is accelerate degrading the rest of the screen so the specific damaged area is less noticeable, but at the cost of making your entire screen dimmer.
The equivalent of having a dark corner to a room and wearing sunglasses in that room so you don't see how dark that corner is because the entire room is now dark.