I had this too.  It's weird.  It seemed to hang on for a few days, but it went away on it's own.  I'm pretty sure it's related to a really low-grade cold, or inflammation (allergy?) in the ears/tubes.  It lasted long enough for me to get kind of worried, like I was going to be one of those chronic tinnitus guys who have it for life.  Give it a week.  Try some Sudafed (the real stuff from behind the counter).  If it's not gone by then, time for an ENT doc.