I have fullness in my ears after loud events. I believe ears become more sensitive once you have tinnitus, and as such can cause swelling in the ears. That or the loudness damaged structures in the ear that would then cause the muffled/full feeling.
Today I was exposed to over 140 db at the movies and both my ears feel semi-painful and full. I can only hope it's the first reason I've listed and not the second.