Ah that makes more sense now
@marta Rhemi, and you are doing fine with your English
it’s difficult to give you any more advice as we can’t give medical advice on the forum, have anyone you’ve seen actually told you what it is? Is it an open sore with infection or just the swelling? I think the best thing you can do is go back to your GP and for a referral to a specialist
You say your last test for diabetes was 2 years ago was that when you were told you were pre diabetic? It may be worth asking for a Hba1c test at your GP. It could be that you have moved into higher numbers since your last test and if your blood sugars are high that can make healing slower & more difficult