I bought a pack of hamburger meat from walmart sunday. Today I made hamburgers and when I took a bite out of my food I bit on something hard... Spit my food out and there was a industrial sized staple in it! Can I sue for this?
You can sue if you want. We live in a litigious society and anyone can sue anyone for anything. That is, however, no guarantee that you will WIN.
So you found a staple. Were you seriously injured? Do you have medical bills or evidence of the injury? If the answers are NO, then that is also going to be the answer about whether you can sue and win a substantial settlement.
You MIGHT be able to go to the store manager and file a complaint, but as Pro says, without the original packaging and receipt, you probably won't get anywhere. They MIGHT offer you a refund, or gift certificate, or free product. But you did NOT win the lawsuit lottery here.