I hit my knuckle a few months ago, still sore but had x-rayed and no break or chips. 4 months +, still pain. Tendonitis, bad bruise? See ortho? Thx

Wait a little longer. Contusion or hard bangs on the knuckles may take 6 or more months to heal. You may have injured the periosteum. This thin tissue layer provides nutrients to the bone outer surface, it heals real slowly!
Yes. You may have injured the extensor mechanism over the knuckle. A thorough exam should help you understand what the problem is and if anything other than tincture of time is necessary.