Regardless of whatever some ER physician told you, you passed out from hitting your head, semantics aside, that is the textbook definition of a concussion. You can call it whatever you want, but you should follow up with a physician at some point to make sure everything is fine. Your family physician is probably just as good as anyone to do this. Furthermore, though the chances of bad delayed sequelae of concussions that are mild are exceedingly small, be aware that they can occur. Should you develop any symptoms such as memory loss, nausea, vomitting, visual issues, passing out without reason, weakness, numbness, incontinence, personality changes, language issues... you need to see a neurosurgeon, or neurologist pronto.