I Go To A School Where We Wear Uniforms, So

I go to a school where we wear uniforms, so my skirt has a hard band that goes around my waist .. I must admit I have been feeling a little crammed in my skirt because of the band being so tight around my waist but I never paid it any mind until one day my waist felt a little sore and when I looked there were marks on my waist, like any normal person I simply got and ointment to put on the sore areas but now that its healed the areas are very dark around my waist and its very annoying please help! thanks