Hi Bhavna,
We wont be able to visualize the difference if its quite less so better to keep a track on arm measurements. Also, our body have a tendency to get adapted to any workout if done for a month or so. So its better to keep on doing variations in arm exercises . This variation can even in sets or repetition of a particular exercise. For E.g. if you are doing Biceps curl and triceps curl for 2 sets of 12 then, change it to triceps overhead curl and biceps concentration for 2 sets of 12 counts. Try this workout pattern.