smell of poo in childs nose & blue lip

i have a 3 1/2 year old daughter. and have noticed recently when she picked her nose she said mummy smell my finger. It smell of poo. i shouted at her and thought she had been putting her fingers by her bottom. But now i have realised she had been picking her nose and that is where the smell is coming from. What does this mean. She had alot of chest infections from about 1 years old until she was around 3. She does have a blue & brown inhaler but doesnt use them anymore. In the last 2 days her bottom right hand corner on her lip keeps turning dark blue, then goes back normal then will change to dark blue again. i took her to the childrens department in the hospital, but they said she was fine & she must of banged her lip. i dont no what to do for the best, because the gp are rubbish and you feel like your wasting everbodys time.  Please help x