It doesn't sound normal to me. You should definitely take the baby to a pediatrician to ask this question just in case it is serious or requires special care. Hopefully it is nothing.
I would get it checked any time there is something unusual in a baby or child. But I have had craking sounds when I bend (in my knees mostly) since I was a kid. My mom never mentioned if I had it as a baby. I think it is genetic and not a harmful thing though.
my son who is now 6 has had creaking bones since he was a baby
he is perfectly healthy and has had no adverse effects from this