Welcome to the forum. Hopefully some of us will be able to give you some ideas on what you are dealing with. From what I can see in the photos I would suspect Feline Acne. It can be quite sore as it progresses, and with her scratching at it it will start to bleed. There are topical ointments on the market that can be purchased and applied that will clear the problem up. Do not use acne treatments for humans on a cat - they can have adverse reactions.
If you are using plastic watering dishes, and feeding dishes - switch to glass. I found this very helful in helping to treat Acne. Plastic has a tendency of breeding bacteria that causes Acne, and the glass is easier to keep clean. I find that the Corelle dishware works best as it will withstand moderate bumps without breaking. Stress and poor quality food can factor into some of the cause for Feline Acne.
One other thing that it might be is Ringworm, and it isn't what it sounds like. It's a fungal infection, and it's contagious. It will spread to humans. I don't think it is but I can't tell from the photos. The best thing to do would be to go to the vet and get his opinion, or someone who is knowledgeable, and can see it firsthand and make a diagnosis.
Animals are such agreeable Friends.
They ask no Questions. They pass no Criticisms.