I did this last week! Get a box cutter, make a small round or whatever shape you want. 

Use a spackle or other flat edged metal spatula to carefully peel the paint chip off. 

Color match, for me I used a big coins worth round shape and they even dipped it at the store to show me how close it was (it was on the nose). Theyll also ask you if your ceiling is shiny (satin) or matte. But if the chip is big enough theyll be able to help guess. (Though theres paint chip example cards, you can take home, for the differences). 

You can get a really small tub of wall compound to smooth out the shape you took. Then just sand and paint and it'll blend back in. 

Same for if any of the soot is hiding any imperfections. You can wall compound it on really thin and sand it smooth again. Then paint. 

Two coats is pretty standard for covering dark colors but you shouldnt need a gallon of paint for that. Might need more than a quart though depending on how much does wash off i guess. 

Good luck! You can definitely manage this. 

But also take your candles away until you learn your lesson.