What Causes Swelling And Pain In The Legs Of A Child?

Hello. Hoping you can help ease my mind with what is going on with my baby girl. She just turned one and symptoms started last Monday. After breakfast we went to play outside. She was walking bare foot on the patio covered concrete when she sat down and cried in pain. I picked her up and noticed her feet were incredibly swollen and bumpy. Believing it to be contact dermatitis, I begin applying cortisone cream 3x a day and covering with socks. Also stopped letting her play outside with out shoes. On Thursday she woke up with an incredibly hoarse voice and seemed to be in pain. I gave her some Tylenol, which helped and brought her in to see her pediatrician. Pediatrician said it could be virus like HFM and advised to apply lotramin. After cleaning everything and continuing on with Tylenol and lotramin symptoms don t seem to be getting better. She has never ran a fever higher than 99, but she seems to be in pain and tired. Sometimes she just sits down in pain from walking! Any ideas? Should I be worried? Thanks! Concerned momma