My Daughter She's 5 Years Old, She Was Bitten By

My daughter she's 5 years old, she was bitten by a bug ( dont know if its a mosquito or something else) she developed a pustule. 5 days later there was a purple rash all over her lower legs and very few on her upper legs, on day 7 she had a left sole edema with pain that she cant touch the floor. There are multiple red patches on her feet and soles and her right knee is mildly swollen and warm. I am really concerned about what this is, she's crying and screaming of the pain even through her sleep, she's somehow relieved when I raise her legs. Any suggestions!!