it could be an old rash or cut . has s/he had a cold recently because i know it sounds horrible but s/he might have picked there nose and the bogie might have gone hard so as she picked it it has cut it
it kinda depends i watch my 2 year old nephew's but it kinda depends if it a neighbor i think no but if it like grandparents or aunts or uncles ect.. then yes because you can trust them