You're speaking with Dr. Michael Salkin. Welcome to JustAnswer. I'm currently typing up my reply.
I'm sorry to hear of this with Kizzy. I recommend that you insist upon a biopsy of that mass. If cancer is, indeed, found, you'll have the closure you need. In the event that that mass represents a different disease process such as eosinophilic granuloma which would be consistent with her miliary dermatitis/eosinophilic skin disease, you'll know that it can be addressed with the same type of steroid that was in the injection.
Please respond with further questions or concerns if you wish.