Suggest Remedy For Black Mark On The Upper Thigh

Hi i have a black mark on my upper thigh. It's underneath my skin and kind of looks like it's in a pore. It's very small and not circular in shape more like a thick line. The pores on my legs are bigger than the pores on the rest of my body and i would say this mark is no bigger than the pore but it's very black possibly blueish tint but more black than anything. I'm very worried it's cancer it's been there for over six months hasn't grown but isn't going either and when i go to try to squeeze it it just sinks into the pore. I went to drs who measured it and looked at it through microscope thing and said he didn't know what it was but to come back in 3 weeks made me even more worried that it's skin cancer. What could it be?! It's definately under the skin as when i go to squeeze it and it sinks in i can see a very thin layer of skin over it...... please help im only 26 and not a sun worshipper but did get badly sunburn as a child as i have fair skin