Been to the physio and he said I have it band syndrome and he has advised me to manage it.
Any advice from you how to manage this muscle
I have this and was given a lot of exercises ranging from stretches for the ITB to core strengthening, gluteus medius exercises and leg strengthening (VMO) stuff to balance my knee.
Check your seat height. Usual to lower it a bit with ITB to prevent over extension of the knee and stop the ITB passing the bone knob on your knee (lateral epicondyle) which causes the inflammation.
Also get feet checked for flatness. My flat feet were causing my lower leg to rotate inwards putting stress on the insertion point of the ITB alongside the knee joint. Custom made arch supports helped.
You might have a combination of any or all these problems so your physio should be recommending which things you need to address. It's taken me a long time to sort and I'm still unsure how it'll go when I do the next 100 miler which is when things usually go awry.
The article linked to by HLab is a very good source of info.
Hope you get it sorted. It is miserable because there's no way to ride through it and nothing to do but wait for recovery once you have it.