Mumps is a viral infection that often cause swelling of the salivary glands in the cheeks, swollen cheeks in children along with fever and so on.
Treatment is mainly symptomatic. Give pain relievers and antipyrectics like paracetamol, ibuprofen for fever and pain. Give plenty of fluids too and keep the child isolated or at home as it is contagious
It may take 1 - 2 weeks for symptoms to fully resolve and it goes on its own.
Mumps can be prevented via immunization; the MMR (Mumps, Measles and Rubella) vaccine. The first dose at 12 - 15 months, booster at 4 - 6years.