Where is this spot? It sounds like a "spot" I found on my upper gum, but I felt the other side and noticed it was there too. I talked with my oral surgeon that was my primary cancer doc, he said they are just palpable and noticeable because of the radiation and recession of my gums.
Not saying that is exactly what you have going on, but maybe it's the same for you!
If the one in Philly says that it's nothing, then you can maybe find comfort, but do you know any of the stats with this doc in philly? Like if he has treated anyone with oral cancer before, or how many and what kinds?
I saw a dentist and an oral surgeon for 5 months, and they had both seen OC before, just not in anyone so young, and they kept insisting it couldn't be until the biopsy proved them wrong.
Best thing is to advocate for yourself, as sometimes, you are the only one that will. But if the doc in Philly has a bunch of experience with OC, and says not to worry, then that is up to you if you trust what they say and just find comfort, or what you do after that!

I wish you luck, and hope it's not cancer!