Ultrasound shows small reactive lymph node in neck which has been there 15 weeks+ bloods are normal and i have been refered to ent. worry?

Don't worry too much: There is a network of lymph nodes in the head/ neck region. When you have a cold or upper respiratory infection, sometimes they become more prominent. They usually go back to normal in time. Sometimes they don't. If they stay enlarged, then it's worth taking a closer look by having one removed and tested. Most times they are just chronic inflammation, but it can be infection or rarely cancer.