This hat is too big

I bought a fitted hat (online) and they only had 2 sizes (7 7/8th and 8) so I figured if I bought the smallest size that I could at least fit it in. I know nothing about hats. I bought size 7 7/8th and its HUGE. I just remembered I am probably a mere 7 or even a 7 1/4th. So what can I do? What kind of crazy online shop only has 2 sizes of a hat, I am guessing the rest were sold out but damnit I was in a rush and did not bother to think about it.

BTW the hat was 15 dollars =/