One year old has red Mark?

Hey just a quick question,

Basically my 1 year old will not sleep in his cot. I have tried every method, today I tried the method of putting him down and leaving the room for a couple mins and if he is still upset to then go in and pick him up.

That didn’t end well. When I walked back in he was banging his head off his cot etc.

He’s now in bed with me and fast asleep but I’ve noticed he’s got a big red Mark on his cheek? I’m worried it’ll bruise or something, is there anything I can do to prevent this or to help it not bruise? He doesn’t seem bothered by it but it looks a bit sore :(

I feel like a bad mother for leaving the room because maybe now he wouldn’t have a big red mark on his cheek😣