I have swollen lymph nodes (cervical) for 15 months, size almost (2cm) no other symptoms, can this be cancer?

Yes: The presence of enlarged cervical nodes present for several months without resolving suggests possible malignancy. If this were due to a head and neck malignancy, the primary would be manifest by now as a large ulcerating oral cancer or a lesion of thyroid. Since no mention of such a lesion, one must suspect lymphoma. Biopsy of node essential for dx.