You can use any anti-bacterial soap. Scrub the area gently and rinse well. Keep you hamster in a warm room or hold him to keep him warm until he dries.
You could put anti-bacterial ointment on the wound if your hamster won't lick it off.
These kinds of lesions can be sebaceous cysts, or something worse, such as cancer, unfortunately. There are of course other possibilities but without a biopsy it is difficult to tell. If your hamster is still active and eating normally than he still has a good quality of life.
I have a hamster about 1 year old. The hamster has black bumps on him. The one looks like it is open and oozing green stuff and it stinks. What could this be?
My hamster is a little over three years old and it seems to be a bone or some sort that I am feeling around his chest wall. He shares a cage with his sibling. In which dont have this on his chest. He continues with normal activities that hamsters do and it do'snt seem to bother him when I touch it but I never felt nothing like this on him before. Any suggestions? My email is ***@****