Basically, you will have to cut the sheeting on both sides of the rib where the sheeting is elevated and then carefully remove the elevated sheeting and also remove the glue so that the surface of the rib is back at the correct level. Then cut out a piece of sheeting that will fit well into the gap/hole where the removed sheeting was. When glueing in the new piece you will probably do best by putting a piece of balsa sheeting under the splice line on both sides; glue the splice under the ends of the existing sheeting first. This will help to make everything even. Using medium CA for this job may be a good idea. Fill in any gaps with your favorite filler, then sand even and you're ready to cover.