Honestly, no one - not even a doctor - could tell you if your son has Lyme or not based on what the bite looks like/whether there's a rash. The bull's eye rash typically associated with Lyme doesn't even occur half the time in infected individuals, so that's not the most reliable indicator.
It's good that you started antibiotic treatment right away, but I would do whatever you can to demand that your son's doctor take this seriously, regardless of his/her own opinions about
Lyme. Get him tested - although please be aware that testing isn't always reliable either (but it helps to have a positive test).
How long is your son on antibiotics for? If it's 2 weeks (that's what I was given when I was first infected 10+ years ago), you may want to ask for a longer run - maybe someone else on the forum can chime in with the recommended dose.
I don't mean to scare you - your son may not be infected at all, but unfortunately there's no true way of knowing for certain one way or the other. Pay extra attention to ANY symptoms - no matter how irrelevant they may seem - that pop up in the next few weeks. If it is Lyme, you may meet some resistance from doctors who don't understand this illness very well, but we've got to be our own advocates.
The most important thing is that you caught onto the possibility right away - meaning you can likely nip this thing in the bud if he's been infected. You may want to take a look the symptom list for Lyme disease (and co-infections), that way you can be alert
to any changes in your son's health - the list is located in the "New to Lyme?" thread www.healingwell.com/community/default.aspx?f=30&m=1606610
I wish you all the best and we're here to help!
Co-Moderator, Lyme Disease Forum