It is possible to cover scars with tattoos but you need to consult with an artist that has knowledge in working with scars. I watched a YouTube video about it and the girl in the video had extensive and raised scars. She goes into detail about the complexities. Certain colors and designs will look better and if you go to an artist that doesn't have a lot of experience with scarring it could lead to a botched job. I'd definitely do research on good tattoos artists in your area and consult with any people that you know who have gotten tattoos.

Receiving a botched tattoo can be pretty crappy especially, if, you end up not being able to cover it.