In a spot of hot water over Home Surgury practice. Advice?

Here's the situation...I practice Home Surgury on low income seniors and people with no health insurance. I do this out of my garage mainly, although will make house visits. My operating instruments are basic woodworking tools, X-acto knives and a Makita cordless drill. I've had pretty good luck... simple procedures like appendectomies, tooth extractions, simple amputations and goiter removals...and would like to branch into knee replacements and gastric bypes after reading up on a few techniques . Business is good, with only a handful of complications and complaints. While performing a routine gallbladder snip and stitch, I believe the battery from my cordless drill became disengaged and slipped into my patient. I can't find it anywhere (luckily they come with two batteries). I haven't said anything to the patient, but now he complains of pain and swelling, the swelling is in the exact shape of the battery. Should I risk a lawsuit, not really being a doctor? Or keep quiet?