I Have A Pimple On My Lip. Because our lips are so tender even a seemingly minor abrasion could cause the area to swell and turn red. Location is helpful with distinguishing.

The herpes simplex virus HSV is a common viral infection that can cause cold sores on the lip and around the mouth. The swelling will go down but you should be careful how you squeeze pimples you could end up with marks on your face. If your body is going through hormonal changes caused by stress puberty menstruation or pregnancy then you may develop pimples on lip.
Could it be a cold sore.
A pimple may sometimes appear on the surface of the lip. They are small fluid-filled swellings that occurs inside the lip and other parts of the mouth. Cold sores are small fluid-filled blisters that can be painful and itchy. See a doctor if any pus throbbing tenderness fever etc.