Can I eat Nandos? Think Their chicken Peri Sauce Is made with herbs

No problems. Try not to nitpick on every little bit of ingredient, and you will be fine. Big picture: herbs are usually used in very small amounts in most dishes, except (as pointed out) in the case of Chinese herbal soups etc. As long as you practise restraint/moderation and not start chewing on a bunch of herbs for a snack, you’re golden. Spicy is ok too, again - as long as you’re not eating ONLY spicy food every meal, you shouldn’t worry. The human body is more resilient than we give it credit for. 😉