My dog Eye was swollen shut this morning!?

Hello, i woke up this morning and went outside to feed my dogs i noticed that my Dog Right eye was swollen Shut with Mucus ...... My emediate reaction was to wash the mucus off with water it got better and he can open his eye now but it's still swollen.....Is there any medicine they sell at stores For dogs with this Problem ? Or any advice what i could do at home to cure this?