So let’s see. Your front door is your main entrance to the world. In terms of you, the way you face the world most of the time. However you are opening it at night, which is a secretive time when no one will notice. This suggests that there is a dark or secret side to your main way of facing your life or facing the world.
Outside? Rotting bones. It takes a long time for bones to rot. Who knows what the bones are or where they are from, but I presume this is a part of yourself you killed off a long time ago. Or thought you killed off. But there it is, when you take a secret look at yourself. A look that no one else will ever see.
Over those bones are flies. Carrion eaters. Pests. They birth maggots. Whatever, they are trying to dispose of the remains of this part of you that you thought you killed off.
So then the huge mosquito appears. Mosquitos are annoyances, and they can make you itch or even pass on diseases. So we have a giant annoyance that has potentially serious consequences although more likely just annoying consequences, except that it is huge, which means those annoying consequences could end up being huge.
You avoid it, but it is sticking its proboscis through your peephole, anyway. I.e., your view out on the world.
I would say that you are dealing with some kind of old problem that you used to experience in ordinary life. You thought you’d dealt with it, but, no matter how hard you try to keep it away—no matter how strong your walls of defense are, it is still out there, and it is growing stronger again. It is now clouding your way of looking at your daily life.
This is probably a childhood problem. I think that shyness or being bullied would be examples of this, although it could be many other things. Whatever—let’s say it’s shyness—it is coming back, and it is bigger than before (suggesting something happened in the intervening time that made this problem more significant—if it were shyness, maybe you got a job involving lots of public speaking or maybe it is now hindering you from finding a mate), and even though you think you’ve made yourself safe from it, it it coming back more than you consciously realize. Hence your dream tells you.
So, what about that? Does that ring any bells or does it seem like complete bullshit? It’s a dream for God’s sake. Who knows? I’m just doing symbolic interpretation on the fly. For the sake of pride, I hope this makes sense. For your sake, I hope it’s nonsense.