I have what look like boils or abscess, differ in size but become very tender and red, fluid can be felt under the skin, they generally stretch the sin and burst on their own but generally mainly blood which is dark red but then as it leaks more it becomes a brighter red, rarely pus. I have diabetes 2 which may have a baring, they usually go on there own but I have quite a few around the pubs bone that have burst but don t go away.