Sore on breast

I had what I thought was a pimple come up on my right breast, right above my nipple, 3 or 4 days ago. i didn't think too much about it but this morning it is noticeably a little larger, surrounded by red skin. & it is painful to touch. I am a 62 year old woman, diabetic & insulin dependent.

I think its a breast abscess and as a diabetic you may be prone to them. Can you contact your doctor for some advice?