Use the "save as".
Hmm, there are LOTS of programs that can open, edit, and save modified
images.
You don't mention WHICH program you are using.
You don't mention why you need to reopen a pic that you just saved [as].
Look in the titlebar of whatever application you are using to edit the
picture.
When you use Save As, maybe the titlebar shows that now you are pointing to
the saved as file rather than to the original file.