The first punch usually wins the fight. Sounds to me like you were in fear for you're safety, you tell a cop that and you should be o.k.. They say you need to be able to turn and run, but it sounds like you really couldn't, so if you tell the cop that you should be in the clear.
You had the FIGHT OR FLIGHT adreniline reaction that everyone/ every species gets. Welcome to the world of finally being a true mammel.