Hello and Welcome to ‘Ask A Doctor’ service. I have reviewed your query and here is my advice.
Probably the red mark you have in your upper back is a
cherry angioma, since you have it for years.
Cherry angiomas are skin growths that are formed from collection of small blood vessels and are very common.
Usually cherry angiomas can slightly increase in size over the years and they can bleed from trauma and schratching.
In my opinion it might have been injuried and that's the cause of bleeding.
However, if it continues swelling, bleeding, increasing in size, or changing color these are reasons to be concerned and you should
consult a dermatologist, for a dermatoscopic examination, or to take a
biopsy and further treatment (electrocauterization,
cryosurgery)
Hope I have answered your query. Let me know if I can assist you further.