About 4 weeks ago i was performing oral sex on my partner and accidentally grazed the tip of his penis with my tooth. he had 1 painful sore on his penis which has now turned into multiple painful ulcer like sores on the shaft that wont heal?

It sounds like he has newly acquired herpes. "Grazing" the penis with your tooth probably has nothing to do with this. Do you have oral herpes (cold sores)? Herpes symptoms usually start within 3-5 days of exposure, sometimes up to a couple of weeks, so that's a likely time frame of possible exposure. He should get care ASAP both for accurate diagnosis and prompt treatment. Good luck.

He needs to see a Urologist soon. In the meantime keep the area clean with soap and water, apply triple antibiotic cream and hold sexual activity.