What are my legal rights if a clamp was left inside of me after surgery?

Yes you certainly have a case because I believe over the past few years there are laws that now require that the surgeons and surgical staff to number and count (essentially take inventory) of all instruments to be used or present in the operating room for surgery.  Before surgery is fully completed (i.e., the stitches in), inventory must be taken again to ensure all instruments are indeed outside of the body.

If you are suffering any pains, scarring, time off from work, and will need time off to remove the clamp, you can most certainly sue.  However, also keep in mind each state now has limits on the amount of recovery due to medical malpractice. Make sure you speak to an attorney who has no affiliation to the doctors or hospital or staff involved in your surgery.  If they do, those attorney/that attorney cannot represent you.