The shell its defenetly infected. Thouse are absesses and are full of infected material. First make shure the turtle has a basking spot, that the water is very clean, warm and that the filter medium is free of decaying material. Next that shell needs to be cleaned and desinfected. Get some toilet paper, put just a bit of betadine on it and use it to applly only on the infected area (also for better results use toilet paper to dry the infected areas so that the betadine can stuck to it). Se if you REALLY GENTLY can rub of some of the infected material. Let the betadine on the wounds for a copple of minutes, then wash the turt on clean water and return it to the tank. Also in a separate bugget you can help the healing by using tetra general topic