I want to cover my nose whenever I'm near my father
Why do you think that you need to cover your nose around him?
He is so smelly.
If you think your father is smelly you can politely confront him alone. He may not be aware of the issue and if you are able to gently talk to him about it, he would probably appreciate it.
That is gross, can't I just be a little kid?
He's your dad and he spent so much of his time and energy raising you as a child. I know it's tough, but you should try your best to work through this with him. I'm sure that there is a way to talk to him about this without it coming off as offensive.