I would go to an ENT. An oral surgeon can do it, but ideally he should have a ct / pet / or MRI to determine if there are mets - usually if it's in the nodes they can be palpated, but as you probably know there could well be microscopic cancer that even a scan can't detect. My concern would more or less be spread to the gums, and jaw first (mandible?) so a scan would be my next step along with a full examination and scope and a second opinion from a qualified ENT who is very familiar with oral cancer. For what it's worth lip cancer is very very treatable and has a great cure rate. Good luck and take care.