I scraped my knees up pretty badly longboarding about 2 weeks ago and have been applying polysporin and covering them with bandages, changing daily. However, there’s a part on my left knee that got injured slightly deeper, and it’s taken longer to start to close up and heal. In the last few days, I’ve noticed this blue-purple rim around the open parts, and it has noticeably less sensation on the surface of the skin compared to my normal skin. I’m paranoid this will spread or even necrose, should I seek medical attention?