u should have just found out that they run smaller. you could have asked anyone who knows jerseys or watched a video. or called the store. anyway u should change it for the large. just my opinion. however I don't love the fit of these new Nikes. I am in between a L and XL bc of the weird fit. My upper body looks great in the L but then it's tight around the belly. However, with the XL the bottom is good but top is too baggy on the shoulders. it's basically made for either lean or proportionately fat people lol. im unproportionately chubby for these. the Adidas were fine - I was a Large all around.