Toe removed due to Staph and still not healed

My 67 year old mother had her toe removed several months ago due to staph.
It is gone and she can not get it to heal.
Her doctor sent her to a open wound doctor that gave her Accuzyme and said that it would help and she having worse pain than before.
They have said that she has exposed nerves and that is what is causing the pain before the cream, but it has worsened since.
What should we do?