Hi, thanks for sharing your health concern with team HCM!
In the present case of painful dark thigh swelling or lump, if I were your consulting physician, I would consider two or three possibilities like:
1. a neurobibroma or dermatofibroma
2. a
hemangioma with recurrent internal bleeding
3. an infected sebaceous cyst
As per your description, it is a benign harmless lesion like a sebaceous cyst or could be common papilloma like some fibroepithelial polyp!
In any case this could not be some serous disease or cancer...!
Take caution not to get injured there as this might invite infection!
If you are still worried, please get examined by a surgeon or get some FNAC like cytological examination or revert back to us.
Hope you got your answer. Please feel free to write to us if any more queries.
Wishing you the best health!