This is a hardware issue known as a Melted Graphics Card.
What caused this;
Due to overheating and poor cleaning, your graphic's card has been thermally damaged.
What does this mean;
The graphics card can still function but does not operate properly, eventually it will stop working altogether and may even lead to a incident involving your entire establishment and the word fire.
What can you do;
Replace the graphics card by checking onto your graphic card's manufacturing website and look for ideal methods to replace or upgrade.
Preventing further issues;
Cooling gel, regular dusting and not overclocking your computer will increase your computer hardware's lifespan. Take care and don't greed over your computer, it isn't invisible on the physical side.