Kim:
Most dermatologist sometimes use cortisone shots to bring about
rapidRapid shallow breathing reduction of large or
painfulPainful menstrual periods acne cysts. Typically, the cortiosne is diluted to a quarter strength or less to limit the chance of indentation. In my experience, such indentation (called atrophy) occurs rarely, even after dilution. This is temporary, you will be happy to know, though it may take several months for the skin to fill in.
If I were you, I would ask the dermatologist about your concern. Determine whether he diluted the cortisone; if he did, then you would best avoid such injections in the future, even diluted. This is easy enough to do, since acne treatment can be quite successful without injections.
In the end, you will be fine.
Good luck.
Dr. R
Dr. R