Wikipedia says of the composition of the lower atmosphere:
Because methane condenses out of Titan's atmosphere at high altitudes, its abundance increases as one descends below the tropopause at an altitude of 32 km, leveling off at a value of 4.9% [the rest is mostly nitrogen] between 8 km and the surface.
and in a separate article
The average surface temperature is about 98.29 K (−179 °C, or −290 °F).
so any combustion would need to cope with a lot of very cold nitrogen absorbing all the heat.
We can find some specifics: still trawling wikipedia we find this page which has a large table which gives the lower flammability limit of methane in air as 5%. Air is roughly 80:20 nitrogen:oxygen, so if we added 20% oxygen to some Titan atmosphere which originally had 5% methane in it, we would get (cold) air with 4% methane in it, which will not quite burn even at Earth temperatures. So releasing oxygen into Titan's atmosphere is unlikely to make a flammable mixture at local temperatures.
What might work is playing a jet of warm ( by local standards) oxygen onto a puddle of liquid methane, or a surface wet with liquid methane. That might push the methane concentration locally up past 5% and eventually reach a flammable mixture. It seems like methane on Titan (with some oxygen added to the air locally) would behave about like kerosene on Earth -- it won't really burn unless you do something to heat and/or vaporise it.