There are many natural remedies and over the counter products that are compatible with breastfeeding.
You can try the following:-
Rest.
Drink lots of water and take hot baths. Run a humidifier.
Take in extra vitamin C from foods, juices or in supplement form.
Echinacea is generally recognized to be safe for nursing moms.
Garlic eaten raw, cooked, or taken as a supplement can help. Raw is always best, though it’s hardest to get down.