Okay, I don't really don't know how to ask this but my lips have two different skin tones?

My lips are like sun burnt and my skin (face) is a different tone. A lighter-ish sort of tone. It used to be the same tone but later my lips started to get dry and chapped. This has been happening for a month or so. I'm on the track team, and contacted my school nurse. She's told me that its due to the fact that I've been running and lick my lips. She told me to put Vaseline on before I run. And I did, it's been about two days? It looks like it's gotten worse. Before, there was no skin tone line difference and my lips were the same tone as my face. And now, there is like a white line around my mouth. Not my lips. My lips aren't really chapped, it's more of my mouth. It kinda looks like I have a big mustache outlining my whole mouth. Help anyone? I think I'll have to go see my family doctor. Please tell me there's a cure and I'll be able to bring back the originality of my tone so that my mouth blends in with my skin tone. The nurse says that it is going to heal back, but it really looks worse.