I've experienced shin splints too while running. Since I'm new to HIIT also, it's to be expected. Many people report that they go away after a breaking-in period, but this won't be the case for everyone, because the term "shin splints" refers to several different conditions. I've never experienced any knots or swelling, just aching/soreness/pain/tenderness. In addition to the tips mentioned in this thread, one other helpful idea which I've seen mentioned many times is to strengthen the anterior tibialis muscle. Correcting the possible imbalance in strength between the calf and shin muscles seems to help a lot of people, from what I've read. So, focus on contracting that muscle throughout the day by bringing your foot/toes up towards your shin with some intesity, perhaps even using some resistance.