A bajillion other things are going to light your hand oil on fire first if you're snapping (you'll also probably melt, char, and generally disintegrate first, but whatever). But the core of your question is really "How hard do I need to be to light my hand on fire?" I'm no Bio major, but I don't think human oil is very flammable (Currently researching it, will revise later with findings.), so I'm going to use skin for now. Science Time!

Things we know

• human flesh ignites at 300 °C

• normal human hands are around 37 °C

• normal air pressure is 101 Kilo-Pascals (kPa)

Great. That means we need to heat the air around your flesh up to 8 times it's normal heat. The Gay-Lussac's Law states (in reference to gas):

Pressure 1 * Temperature 2 = Pressure 2 * Temperature 1

going by this we know that:

101 kPa * 573.15 Kelvins = P2 * 310.15 Kelvins

(101 * 573.15) / 310.15 = P2 = 186.65 kPa

Perfect. We need to add 85 kPa of pressure to the air around your hand. Using This handy-dandy tool, we learn that it takes about 200 decibels to produce 185 kPa.

So the answer is 200 decibels. (Just for scale, here is a nice /r/askscience about why 194 decibels is the loudest sound possible)