I wouldn't worry a whole lot. My son had high lead levels, but not lead poisening. We found it when he was 6mo. We still aren't sure where he got it from as none of us or even his little sister got it when she was born and living in the same house and conditions. We dealt with it for about 9mo to a year before he was 100% free. He has no health problems or delays.
If your worried, start feeding him foods with higher iron, calcium, and zinc. Then have him tested at his next appt. If he does have an elevated level, all they are going to do is tell you to start feeding him these types of food ( they absorb the lead from the body) and eliminate the source... since you know where the source is coming from that will be easy for you.
Good luck