GARBAGE DISPOSAL QUESTION

Would appreciate a plumber's answer to my question. My sink is divided in two with the "regular" sink basin on the right and a garbage disposal on the left. Although we never put anything in the disposal, I noticed the water was draining very, very slowly. I read on the internet that loosening the bottom center nut with a garbage disposal hexagon wrench might help. I bought the required wrench did exactly that -- and it worked, I'm happy to say. But here's the question: should the nut remain loose now? It was tight and after I loosened it, the water drained, presumably after I dislodged something. But when I tried to re-tighten that nut with the wrench (which I thought I had to do) it just loosely turns. Should it re-tighten??? Sorry if it's a silly question but plumbing is not my thing. Thanks.