My son is 5 he was at the park yesterday evening. He was wearing sandals this morning nothing but when he back from school his left ankle and leg is swollen he is complaining of pain. Could it be a bite or soft tissue injury. He was itching on it last night.
It is really hard to comment on this without examining. The itchiness could be due to Chat Doctor.  On the other hand, the swelling could be due to some insect bite or due to some sprain of the ankle. I would strongly insist that you visit a doctor and get the child examined so that appropriate interventions may be taken in time. Hot and cold compress should give the child relief.