On the head of my penis, there has been a blackish color on the area surrounding the opening and a portion of the head itself. theres no pain involved?

Could be anything : It is difficult to comment without actually examining the lesion. There is always a chance this may be a tiny hematoma or blood clot from injury or rough intercourse. Or it could be something more sinister such as a melanoma. Please see your doctor for further evaluation

May be benign: This may be a benign skin problem but it would be best to have it clarified with your physician or a dermatologist or a urologist