Praise be to Allah.
The basic principle is that treatment and nursing of women should be done by female doctors and nurses, because of what is involved in treatment of looking and examining. But if there is no female doctor or nurse, it is permissible for that to be done by a man. But there is no doubt that finding female nurses is something easy and readily done if the people in charge of the hospitals want to do that. It is very sad and unfortunate that some hospitals delegate female nurses to take care of men and male nurses to take care of women. This is indicative of weakness in religious commitment and a lack of proper supervision, and a lack of attention to the rulings of Islam.
Hence we advise you to try hard to limit your work to treating men only, even if that means moving to a ward where that is accepted. If that is not possible, then there is nothing wrong with you continuing in your work and treating women, on condition that you adhere to the following guidelines:
1.Do not look at anything except that which is necessary, and fear Allaah with regard to that. You can be certain that Allaah is watching you and recording your deeds.
2.Do not touch any part of the patient's body without a barrier. So you should always wear gloves when treating women, and even so, do not touch anything but that which it is necessary to touch.
3.Limit your talking to the female patient to what is necessary.
4.Do not be alone with a female patient in an examination room or x-ray room and so on. Rather she should have her mahram or another woman with her, whose presence leads to avoidance of improper conduct, such as her mother for example, or other female patients.
We ask Allaah to forgive you and make things easy for you.
And Allaah knows best.