materially false" -- that is, a significant and relevant lie -- you would be guilty of perjury. Perjury is typically a felony and in federal civil cases such as copyright infringement, the perjurer may be subject to fine or jail time.
What should you do? You may believe that your statement is not particularly significant or relevant to the case but we think the best route would be to notify the attorneys who prepared the document that you signed and tell them of your error. There's always the possibility that you misjudged its importance and relevance and they would want to decide for themselves.