Is it possible to remove a scar on the back side of my head from a hair transplant surgery? If, so what is the best option?

Yes this is absolutely possible.  You can either have the scar excised and closed with the newer techniques that allow hair to grow out of the scar.  You can also have an FUE procedure and have grafts placed into your scar.  

Hair transplant scar repair can be achieved by inserting grafts extracted through Follicular Unit Extraction( FUE) into the scar tissue. With this approach, the scar can be sufficiently hidden so that it is no longer visible. Here is an example of a patient from the Dr.U Hair Clinic who underwent a strip scar repair while replenishing the areas of non-growth which resulted from his previous procedure . His before and after photos show that inserting Follicular Unit Extraction grafts into the rather large strip scar was quite effective at concealing it. In fact, many of our patients can wear a short buzz cut after this type of scar repair.

You generally have two options: (1) Scar revision - at BEST this will give you about 50% reduction in width, (2) Scalp MicroPigmenation SMP - this will not remove a scar but will help hide the scarSee video

Once a strip surgery produces a scar is performed, you cannot remove it.  The best you can hope to do is to camouflage the scar by adding hair to the scar by follicular unit extraction, applying small dots of pigment by scalp micro pigmentation, or to reduce the width of the scar by a scar revision.  Strip procedures also cause a misdirection in hair growth alignment, as well as, joining hair of different caliber along the margins of the scar. These problems of misalignment and differing hair caliber cannot be resolved.  The best solution is to avoid a strip harvest procedure entirely.  

Scar revision surgery for bad hair transplant scar.I have done this sort of revision surgery for a bad hair transplant scars for 35 years. This car is never totally remove it should be a fine line when done. See a very experienced surgeon for this