I need help fast

[x240xdrifter]

hey, my name is will and I drive a 89' 240sx ka24e with a 130,000 miles on it, the other day I went to a empty parking lot and just had some fun with it, just getting use to the feel of the car, one my way home I notice it started to knock upon accel. around 1600rpm. went I got home I shut it off,I flipped out and checked the engine which was extremely hot, so I let it cool overnight, the next day I checked my fluids and to my dismay, the oil was very low, grant it there was still oil in it, but not alot, so long story short, the engine now knocks, what could be wrong, how bad could this be, how can I fix it?, btw, the engine runs, but knocks alittle and it starts on its own cranking power., but I let it sit overnight again, and it the starter doesn't even click rapidly, I'm guessing the battery needs to be jumped maybe, its also below 32 degrees out I dunno I need help, thank you so much for any help

[x240xdrifter]

Its got a loud knock going, but it will go away if im in 5th gear and on the gas a lot, but only going like 25mph. So is it running really lean?. What should i check first? the knock seems to start around 1500-2100, could the MAF senosr be bad?

[Ni2s4s0aSnX]

Oil leak or burning oil.