You do not ever have to report someone, you may, if you choose:

From: https://www.socialworkers.org/pubs/code/default.asp

No one else can report what happened to you though, except you; they were not there and were not part of the problem and you are not a child. Your current social worker may give her opinion of how the other social worker handled things but that's about it because she does not have first-hand information of what was said/done, why, responses, etc.