Sooo...you're saying that it was a "piece of the spring that sets inside of the valve spring"?? Meaning you have dual valve springs...and a piece of one of the inner springs fell off and somehow got down into your oil pan? I don't see how that is possible. IMO, it looks like a piece of a bearing...or a sleeve of somesort...
Regardless...you need to find out exactly where it came from and DEFINITELY fix this problem before starting your motor. That piece of metal came from somewhere inside your motor...and it is supposed to be there... If you think it has something to do with a valve spring...simply pull your valvecovers off and look at your valvesprings. Keep us posted.