My 8 year old daughter come home from school and said her left side of her face hurt and hurts when she swollows what could it be?

Lots of things. It could be a dental abcess or a cold sore. It could be a muscle spasm or a sore/ulcer in her throat (usually from a virus). It could be a problem with a salivary gland or tonsils. See your doctor if it doesn't go away in 1-2 days (or if it starts to get worse or if there are new symptoms).