u/FlatInterview9038

Hello. I am a beginner to keeping african dwarf frogs and I am unsure of what this spot is on my frog. I have two frogs, and I am going to get another soon. I have a 10 gallon tank with wood and live plants. I feed them frozen food every other day. I just tested the water and did a water change, and everything seemed to go okay. When this picture was taken the frog was singing/croaking. The only thing that I think could have cause this injury was my other frog accidentally biting him during feeding time. Please let me know if I am doing anything wrong or if you have any idea of what the injury could be.