Sketch is not working with Nano perfectly like Mega2560

Yes, I have removed all the connections before running it..
Another behavior I have noticed that when I run code, LED on the board (13) blinks even though I have not coded for it... is it normal!?

I have attached my circuit herewith, unfortunately I am not able to download the software to draw the circuit and in online drawing tool, nano board and my sensor was not available....