It's one of the few immediately hittable features with a lasting sensory effect. I've never been punched in the tongue, but i imagine it would feel different from most other places.

I think it has to do with the fact that when you're hit in the nose, you experience all the other normal "getting hit" effects, but in combination with them, there's also the way it affects your smell perception and the way your brain processes non-smell signals as smells. There are a lot of nerve endings in that area the typical of which is interpreted as smells or nuances of smells, and after a hit they're firing due to swelling, damage, etc.