What Causes Inflamed Redness Around A Cut At The Knee Going Down The Leg?

Hello I have a long cut going from about 2inches below the knee all the way to my foot it is about 1 inch wide going down. I have been wrapping it for work with gauze and bandages and putting neosporin antibiotics on it, although today I didnt I just wrapped it and now the scab is surrounded by a red border.