A pimple on your lip can last for about 1 to 2 weeks, but if it is caused by herpes (cold sore), it might take longer. Cold sores are typically caused by the herpes simplex virus and may recur throughout a person's lifetime. If you suspect that what you have might be a cold sore or any other concerning skin condition, consider consulting with a healthcare provider for proper evaluation and recommendations tailored to your specific situation.