No! it is never a good idea to do so because firstly the scar tissue is different from the rest of the skin, it is rough and less porous, and secondly, the pigmentation of the two would never match. But, if you still want to consider going for a tattoo to conceal your scar, consult a dermatologist, let them analyse the depth and type of scar, and only after getting consent from your dermatologist, go ahead with your plan.