Although steroid shots into the joint are intended to provide a local effect only, there is the possiblity of some systemic effects. When someone takes steroids (corticosteroids) orally or through a vein, the most common side effects are increased blood sugars, increased appetite, insomnia, water retension, psycosis (we call it steroid craziness) just to name a few. It's entirely possible you may be having some of these effects as evidenced by the "speed" feel which is likely an increased blood sugar and heart rate, and the insomnia is a given.