How do I remove these marks?
 

I recently purchased a hard to find sonic adventure figure from a retro store near my house and it has a couple of white line marks over it and I've tried to get them off but I just can't.

I could only scan the figure as my camera isnt working :p Images are attached

That looks like the paint got scraped off at those points, so I would wager the only fix is to paint over them but it might be more hassle than it's worth since you could, in theory, mess it up even more than those lines do.

Ok thanks!

Looks like the paint got scraped off to me also. If it were marker or some other surface marking you could use alcohol or rub toothpaste on it, or possibly just use a little water and a magic eraser.

It is white plastic with blue painted over. It is cheaper to put one coat of blue over white than 4 coats of white over blue. White is a difficult colour to paint over a dark colour.

Three choices....
Live with it
Paint it yourself
Have a professional here paint it for you