What Could Cause A Painless Black Patch On My Right Eyelid With No Injury, Given My History Of Hypertension And Eye Allergies?

hi, i woke up woke up to fin a black patch on my right eyelid not near nose but other end. It is not painful nor raised but i am concerned considering i did not injure myself. my eyes do get itchy with allergy in cold places but this is something new. i m concerned as initially i thought it was a blood clot. i m hypertensive