Are two lymph nodes each one of them is 1 cm in size, matted, movable a cause for concern?

Could be: It depends a great deal on the cause. Since they are quite small(may even be normal), i would watch and check if they are growing in size any further. If they are not growing over the next few weeks/months, they may not be cause for any concern. But if they are enlarging then you need to go see your doctor for a medical examination soon.

Monitoring Centers: Lymphatic system absorbs/carries things too big to go into the arteries/veins like bacteria eaten by white cells/digested food. Lymph nodes "taste" the lymph everywhere for bad stuff like bacteria/viruses/cancers, etc. When it detects a problem, it alerts the immune system and your body reacts. They enlarge in response to the inflammation they create when they react. They shrink when all is well.