Part of my hand feels numb and my arm just doesn't seem as strong as it should. Could this be from a pinched nerve?

Yes. The nerves to the hand could be pinched at level of the cervical spine, shoulder girdle, elbow, or wrist. If an acute injury is not causal, look to the shoulder. Raise you arms to the surrender position for a minute or two. If this arouses tingling in your pinky finger, get checked for thoracic outlet syndrome. If this is the problem then physical therapy, & not surgery, is important.
Yes. These symptoms may be due to a pinched nerve in the neck, shoulder, arm, or wrist. Sometimes the pinching may be positional (for example, you may be putting pressure on your elbow by leaning on it, which will pinch the ulnar nerve). If it is happening frequently, a nerve study may be helpful to help determine your diagnosis.