When I was 12 I got really bad sunburn on my lips in Mexico. It blistered but eventually went away. Ever since then I have had yellow spots on my top lip, which im assuming are sunspots. Luckily, you cant see them (they arent on the part of the lip that shows) but lately it seems that they are slowly creeping up my lip.

Does anyone have any idea what I can do?

When I was 12 I got really bad sunburn on my lips in Mexico. It blistered but eventually went away. Ever since then I have had yellow spots on my top lip, which im assuming are sunspots. Luckily, you cant see them (they arent on the part of the lip that shows) but lately it seems that they are slowly creeping up my lip.

Does anyone have any idea what I can do?

You really should see your doctor. Any time a mark on your body changes, you should ask a doctor. Especially with marks that involve the sun.
I don't know how old you are, but if you are young and are growing, and the only change you notice is a difference in location and not size, then your lips might be growing. I have numerous scars on my body that aren't in the same place as when I got them.