Given clavulanic acid potassium + amoxicillin trihydrate forte for tooth removal. terrified of side effects, how soon would i notice them?

Almost immediately: This is a penicillin derivative that bis prescribed millions of times daily around the world.In 4 decades of practice the only reactions I saw happen were minor.

It differs : Varies from first day up to really long time after stopping the medicine, example of the immediate is diarrhea, example of the late could be rash.

Side effects: All medicines, whether prescription, OTC, or supplements from a half food store, have side effects. You have to evaluate risk:reward ratio. The risk of side effects from the meds you have been prescribed is very low. The reward is reduction of risk of violent infection. I'd go with your practitioner's recommendation.