Im a bit of a hypochondriac but i may have eaten a small amount of tin foil in my food, please talk me off the ledge ?

Do not worry: It will most likely pass right through your body unchanged

Relax: You are exposed to tin on a regular basis in foils, cans, the earth, etc. . Thankfully it is poorly absorbed by humans/animals. In the 3-4 days it needs to pass through your system ( if it was even there) it would not provide you with a significant exposure. There are some professions where tin exposure is a heavy metals risk & there are ways to monitor/treat excesses. Your event would not qualify