2 days ago, i scratched the outside lining of my lip. when i did a small red pus filled bump formed. its scabbn ovr now. was it a cold sore?

Hard to tell: Is it itchy or painful? Were you sick? Have you had cold sores in that area before? The only way to be sure is to have your doctor look at it. Either way it's not serious. If it remains for over a week it was probably a cold sore. The picture is of a typical herpes simplex cold sore.

Can't say: Cold sores are painful liquid filled blisters that can occur on the lips, roof of the mouth or the gums which are usually caused by the herpes simplex virus (HSV-1). Tingling &/or pain can herald the oncoming of cold sore 1 to 2 days prior to eruption.