If you suspect a small cluster of bumps on your genitals may be due to a herpes outbreak, it is recommended to start taking Valtrex (valacyclovir) as soon as possible. Early treatment with antiviral medication like Valtrex can help reduce the duration and severity of outbreaks.

Please consult with a healthcare provider or physician for proper diagnosis and guidance on when to start taking Valtrex. They can provide personalized advice based on your specific situation and medical history. It's always best to seek professional medical assistance when dealing with potential STI symptoms like genital pimples or sores.