You will almost certainly be working in a hospital now. We expect that you will be in full time employment and you do not need to resign from your post until you have received a firm offer from an NHS trust in the UK and your visa is processed.
You may need to tell your hospital you are applying to work in the UK as we will seek references from them at some point. Some representative of the hospital will be one of your referees.
You are not obliged to be in work at this moment. You might recently have left a post and this application is a part of your future career decisions.