My dentist noticed a growth on my tonsil and said it was cancer? Is all/any growth on my tonsil cancerous

Please visit your primary doctor for a checkup. He will probably send you to a specialist for definitive tests to ascertain if it's really cancer.

Of course we can’t diagnose you online. You should start by seeing an ENT for a proper examination and diagnosis.

You won't know for certain unless you see a doctor and get tested so don't dither on this one.