My 2 year old grandson was running last night and hit the right of his head above the on the corner of my dresser...immediately a nickle/quarter size bump can up. He cried a bit and continued to play, I waited 2 hours before allowing him to sleep, he had a good night sleep and up this morning at 8:00 and the bump is gone. He ate breakfast, been playing, watching cartoons, however, he has been sleep since 12:30, woke up at 2:20 for a minute, now gone back to sleep, should I be concern?