My Son Is Almost 4 Years Old And On Sunday

My son is almost 4 years old and on Sunday he bumped his head with his little cousin and got a bloody nose and we clean it and almost immediately it stop bleeding but last night he was getting ready to go to sleep and his nose started bleeding again and just now he started bleeding just a little and I don't know if it's normal or should I be worry?
It didn't seen to hurt so I don't know that to do?