I read that steroid therapy can cause bone and height loss. i got one prednisone injection for muscle soreness. could this cause height loss?

Wouldn't worry: At age 20 you are done growing taller. Therapeutic steroid use (daily high dose) during childhood can make a kid unlikely to achieve their expected genetic height, but you are done & simple occasional steroid use will not make you shrink.

Not typically: Bone loss and subsequent loss of height from steroid use is usually associated with osteoporosis. Osteoporosis is a complication from long term steroid use, but would not usually be associated with a single steroid injection. Thank you for your question.