I am pretty sure this will pass, but I just wanted to share my feelings. I am not new to nursery care. DS1 went from tiny to school age, DS2 is nearly 2 1/2 and has been going since 9 months (part time).
I know there are times when they are unsettled (after a holiday, change of room, change or carer), I just find it hard. My DS loves nursery and normally either runs off with a cheery wave, or has a wee cuddle before finding something to do. For the past few days though he's settled down to do whatever it is but hasn't said goodbye. Instead I get a sort of aloof display of indifference. I keep myself cheery, I don't keep going back and forth.
A month ago I left him with my sister for a week when I was in LA for a meeting. He was fine, but has been somewhat more clingy with me and can get concerned if I leave unpredictably. He is also moving up to the next room at nursery.
I'm blathering, just wanted to talk really. Back to work then.