Do you have a control negative (H2O)? If the band also appear with the control negative, it means your preparation is contaminated by gDNA I think. Let see in the topic " PCR Contamination issues" and verify step by step.
we didnt make negative control Thats why we are not sure it has contamination or not ! In the slide of ARM-PCR , we confused why do we have a light bright band underneath the 100bp band in the ladder well dear
Hope to hear from u soon