DS head making a dent in cot mattress - is this a problem??

[BristolRabbit]

Hi all, just wanted some advice as DS (ten weeks old) is making a dent in his cot mattress with his head. I turned it over last night thinking it must take some time to create, but there was a new dent there this morning! Already!!

Does anyone think this is a problem for him to sleep with his head in a dent? And should I take the mattress back to John Lewis - is it faulty? It is their mid range cot mattress!

thanks for any advice!!!

Ds1 made a inprint on his mattress (it was foam) think it is normal where they dont move alot when tiny.

My four all made dents in their cot mattresses (new mattress each time) with their heads so i guess it's fairly normal.
I don't think it should be a problem for him, my boys sdents never got too deep.