Sprained my ankle 2 weeks ago. Pain is right behind ankle bone. Dr thinks it's a torn ligament but didn't ask for mri. Is that normal /should I get one?

Probably. Best imaging test to diagnose injured tendons and ligaments is mri. Your doctor may think that knowing for sure what the injury is will not change his treatment and therefore does not want to do the study. Need to ask him or her why not.