My daughter has knock knee, which is not the same as bow legs, but still a leg problem.
We have been told she will grow out of it also, but she needs to be seen by a physio (and has orthotic insoles in her shoes to help with her walking) and also an orthopaedic surgeon, who will assess her every 6 - 12 months until she either grows out if it, or she will need an operation somewhere between 8 and teen years. Not sure yet if she will need it, but the timing will depend on the severity of her knock knee.
I don't say these things to scare you at all, this is just my little girl.
So I would say YES get it checked out. At least you will have a clear mind that you have nothing to worry about (if it's nothing) but if it is something, then you will be taken care of.
I would get referrals to a physio and a paediatrician. (My daughter has also seen a paediatrician, who has then referred her on to the orthopaedic surgeon - she doesn't see the paed any more)
Also nonnuls - I get annoyed by the amount of negative comments. I try to dress my daughter in 3/4 shorts or longer skirts where possible because I get tired of all the comments and people recommending what I should do with her legs. As if I don't spend enough time hoping and praying she will grow out of it. One person even recommended I get her one of those braces similar to the type the people with cerebral paulsey used.