Of course, worms themselves are not so bad, but it is all about common perception. Because worms feed off of dirt and grime, and only come out of the ground in weather that we usually find muddy and disgusting, they are seen as despicable creatures, and as a dream symbol, this perception is not much different. Dream meanings of worms usually involve the way that you perceive yourself, for example, the meaning of dream about worms if you see them on yourself is a depiction of how you see yourself. The worm represents a part of yourself that you do not like, or that you think is disgusting.
Another possible dream meaning of worms is that you are dealing with self esteem issues. Perhaps you have just experienced something that lowered your self esteem. Maybe someone called you a name, or maybe you were rejected by someone. These could be some of the reasons that you might have lowered your self esteem all of the sudden, and that you might now be dreaming about worms. This dream interpretation is the most common one because the worm is seen as a weak creature.
There are a few entirely different dream interpretations that involve worms though. If the worm is in some way feeding off of you parasitically, or somehow attaching itself to you without your permission, this could symbolize a bad relationship. This doesn’t necessarily have to apply to a romantic relationship, though it could. Worms are infamous for attaching themselves to their victims and feeding off of them slowly (if they are the parasitic type of worm). This could mean that the worm in your dream symbolizes a person that may be mooching off of you. They could be taking advantage of your good nature and/or exploiting your kindness for their personal gain. They could also simply be using you to further their social agenda, such as being friends with you only to get introduced to the rest of your social circle.
Worms have a bad reputation and there is nothing positive that can be said about them when they are in your dreams. Even if the worm is attached to someone else in your dream, or bothering another person, it may still be a sign that you see that person in danger, or feel that they are not taking care of themselves to prevent people from taking advantage of them. These interpretations equally apply to your perception of yourself and your perception of others. It all depends on where the worm is in the dream. The main point to remember is that no matter where the worm is, it is always a bad sign.