I am sorry your dogs eyes are sore. There are many things this could be, from a simple bacterial conjunctivitis to an ulcer on the eyeball surface, so it is important if it isn't resolving then a vet checks the eyes as ulcers can cause serious issues.
Sometimes if stubborn antibiotic drops are needed which can only be prescribed by your vet. If your dog is happy and comfortable and not blinking lots then you could consider a couple of days of T-bag bathing, so using a cold wet T bag bathe the eye (closed) for a few seconds and then use the bag to wipe any discharge away. The tannin in the teas is really good for mild inflammation of the eye. Ocular lubricants can help and you can get these from a chemist, these are basically thickened water to help moisten the eye.
See how it goes, if its worsening or not shifting then see your vet