Is that light brown bulb looking thing your seed potato? If so then you planted wrong. Your seed potato should be about 4 inches deep and as the plants grow upward you pile dirt on them. This is called hilling. What you can do is carefully and genty remove the entire root system and plant growth. Then remove all but about 6 inches of the soil and place the potato roots and plant onto the soil. Then cover up with soil to about 3 inches deep. As the plant grows add more soil.
If that brown bulb thing is not your seed potato it is a type of mushroom and is harmless to your plant.