My Daughter Fell A Week Ago And Skinned Up Her

My daughter fell a week ago and skinned up her knees. She didn't treat the wounds until the next day. She put Sayman Salve on them, then the next day put medicated bandages on them. Today, one of the injuries has a red line going down from the knee. I looks just like a vein. Is this an infection in her blood stream? Is it serious?