Hi my hamster has a lump on hur back pow I just cleand it way sult and water help thanks all

What you are doing is good.
Just clean it with salty, luke warm water several times a day.
The salt will help both dry it out as well as disinfect it.

What does the wound look like?
Do you think she has hurt herself or is it more and an actual lump?

Does she run in her wheel a lot?

What kind of wheel is it? Does it look like this?

Attachment 24122

We had this happen often when we had a metal wheel. The hamster runs and gets it's paw stuck in the wheel.

I recommend plastic wheels like this;

Attachment 24123

Keep doing what you're doing. Watch for infection.