If your dentist didn't give you a prescription mouthwash
to use, simply use warm salt-water. It's important to keep the area clean, and brushing might be a bit uncomfortable for a few days.
More importantly, however, swish very gently, so you don't disturb with wound. Ideally, hold the rinse in your mouth and slowly tilt your head back and forth, instead of gargling or swishing vigorously.