Does yoga usually help sports injuries?

Yes! Yoga is a great way to improve your strength and flexibility, both great ways to improve (or prevent sports injuries). Your local y or even your community center will offer low cost classes. There are different type of yoga the one called hatha yoga has movements that involves body movements and streching which helps.
Sometimes. While yoga can certainly have benefits to some (stretching, therapeutic, meditative) it can also pose risks. Some prior injuries or weak spots may become more sensitive or inflamed. Prolonged head-down positions can particularly be risky for those at risk for or in various stages of glaucoma. Check with your primary doctor and/or ophthalmologist to better evaluate before starting a new exercise.