Blood on Sheets

So I woke up to like a quarter size of blood on 8 month olds sheets this morning. I can’t find it anywhere on his clothes, his nails, his nose looks dry, he has a small scratch on his nose he has had a few days... so not sure if he re scratched that and maybe it bled? His ears don’t look like anything happened...

Is that concerning? It sounded like he coughed once or twice this morning.... but I think it was from gagging on the pacifier. Not sure if I should be concerned or just watch it. He’s 100% fine otherwise.