Having originally trained as a botanist, plants always feature in my world-building and it can be fun to come up with authentic-sounding herbal remedies to add flavour to any fantasy mediaeval-style setting (or indeed to research genuine herbal remedies, a copy of Culpeper's Herbal can be useful). That's probably going a bit far for most people, so here's a delightful list of an hundred healing herbs to drop into your game.
Many of the 'remedies' listed here were used in mediaeval times, a few even worked. It's up to you to determine how effective they'll be in your campaign - take #95 Potato: a potato carried in the pocket cures toothaches and guards against minor ailments... to the modern mind this is pure superstition, but in your alternate reality, perhaps it really is effective!
Here's another example - #52 Peppermint: rubbed on afflicted areas to relieve aches and pains; when worn or consumed as a tea, mint cures stomach ailments; added to healing potions and mixtures... well, a mint tea can be settling if you've just eaten a rich meal.
As you can see, it's more than a mere list of herbs, the sort of advice that the village wise woman will give as she hands it over is included too, so you can introduce these as appropriate, and deliver suitable in-character patter. Mediaeval apothecaries also practised herbalism and were consulted much as one might have a chat with a pharmacist today, and an apothercary shop can be a flavourful addition to a town or city in your campaign world. At least after reading this you'll have some idea of what might be found on the shelves.
I'm sure I don't need to remind you that if you are poorly in the real world, go see a medic (or a REAL medical herbalist) for your remedies, do-it-yourself herbalism is not a good idea unless you are very certain of what you are about and sure of your plant identification.