You can actually see a small dent behind the bridge on the previous pictures (it wasn't there when I applied the stain so I must have knocked it at some point - whoops).
I read in one of the other threads that you could steam small dents out so I gave it a go... and it worked brilliantly.
I put an incredibly small dab of water just on the mark itself, stuck a cloth over it and held an iron against it for about 5 seconds and that was it. I had no idea that you could do that. Thanks everyone!