Sprains and strains

The difference between a sprain and a strain is that a sprain injures the bands of tissue that connect two bones together, while a strain involves an injury to a muscle or to the band of tissue that attaches a muscle to a bone.

Sprain Example: While running, your character trips in a hole, falls, and sprains their ankle
Strain Example: During exercise, your character pushes it too hard at the weight machine, and stretches or over-extends your muscle

The main treatment (first aid) for all sprains and strains is colloquially known as "RICE": Rest, Ice, Compression, Elevation. A more severe sprain or strain may require evaluation by a doctor. Joint or extremity splitting or immobilization may be needed. Some severe sprains and strains may require surgery, and if not, may still take months to heal.