My baby measured 5 days smaller should I get concerned?

Nancy
I went for a growing scan last week , the doctor told me everything is fine but she took so long for measuring my baby head she said the head is 5 days smaller she didnt said baby is 5 days smaller she said the head .
She also said do not worried about you tell me how ??? You just told me my baby is chanky he's but then is head is smaller!
So I send everything to my doctor in Italy and he can't really said anything because he want see me but I can't fly anymore.
So is any of you have been told something similar ?? 
She told me to not concern about it but I'm thinking of my baby 👶🏻 head all the time !