Is freezing of windows normal in airlines?
Was it anything to be concerned


No


  Should I have brought it to the notice of the airline crew?


Yes, but not because it is a safety issue. Tell them so they can deal with it to give the next passenger a nicer experience.

What is happening is no different than a glass of ice water sitting on your kitchen counter. The warmer side of the glass (the outside) becomes cooler because of the cold on the inside and it transfers that coolness to the surrounding air. That surrounding air cools enough to cause the moisture it contained to condense into liquid that sticks to your glass. If the glass were cold enough, it would freeze that condensation. The window on the aircraft is that cold so the condensation freezes.

There is a mechanism under the window to keep this from happening. It is a jar of desiccant that absorbs all moisture (dries the air) in the window area so that there is no moisture to condense in the first place. Often, there is a tiny bit still.

As the desiccant absorbs moisture from the air, it retains it. So periodically, it gets saturated to the point it can't absorb anymore and the desiccant needs to be changed.

Either the desiccant in your window needed to be changed or moist air is bypassing the desiccant on its way to the inside surface of the window. Normally there is a seal between the outside window and that thin plastic window you can touch and the only way for air to get in or out of that inter-window area is through the desiccant. Your window may have a broken seal allowing moist air to bypass the desiccant. 

Either way, it is a system designed only to keep the window from forming ice so the passengers can look out the window, it has no safety or structural consequences.