How to get rid of track marks after derma rolling ?

I'm sorry to hear you had a undesirable outcome. By 6 weeks one would expect the majority of the healing of the face to have taken place though marks like yours will continue to fade with time. I would consult with a dermatologist as to the best course of corrective action. 

The best way to treat track marks is to avoid them in the first place. There are reports in the medical literature about track marks appearing after treatment of "bony" areas on the face such as the forehead using longer 2.0 mm needles. However, aggressive home treatments using 1.5 mm needles over "sensitive skin" areas with a derma roller may also be risky. Derma rollers, when compared to medical micro-needling machines used in the office, create a more erratic pattern
of "tears" through the skin rather than the clean, more evenly
distributed punctures seen with the machines. At this point, only time will tell you if these marks will go away.