You might just be dehydrated. Drink lots of water, or maybe even Gatorade (or Zero) to hydrate and load up on electrolytes. Then relax for a couple hours.
Who is "They"? If it is immigration that told you, I would think you should be fine. If it is your school telling you, then maybe they can give you a document to say there is a delay in processing? And in that case, just don't be in a situation to be asked for your passport/visa??
But again, this is a new scenario for me, so I wouldn't know