Any wound that has red lines leading from it needs urgent attention. This is a sign that a potentially serious infection has taken hold. It should never be ignored or treated at home. IV pennicillin or similar may be needed. I once worked alongside a young man who had a sore finger. I saw red lines leading up his arm and advised him to go to ER. He nearly lost his arm because of the infection. Never ignore red lines leading away from a sore or cut!
Excellent point to mention. To me, that's such a common sense statement, but many don't realize that.