It’s not uncommon for children to run a mild fever following an immunization injection. A fever is an overall increase in body temperature that is above the normal 36°C to 37.5°C (96.8°F to 99.5°F).
Sometimes children will try to hide pain or are simply unable to express that they are in pain. However, when children do admit to being in pain, they aren't lying. A child's pain should always be taken seriously. Pain is subjective and what you may not think is painful, your child might.
Break down information into small parts. Explain things slowly and repeat facts as often as necessary. Validating your child's pain is important.