I'll add to all this advice since I had a young show bull develope the same thing about a month ago. This lumps or abcesses usually develope in a lymph node just below the jaw, the cause can be one of many things. The result is an infection in the lymph node, it will be hot and rock hard, sometimes the ear will droop slightly, more often than not the animal will act normally and eat as if it doesn't bother it.
At this stage while it still hard you can't really do anything about it, give it time and it will eventually form a soft spot somewhere on the lump and will burst and drain some fluid. At this stage you can squeeze the puss out, it will be very foul smelling and look like cheese spread. Then flush the wound with a 20% hydrogen peroxide that is diluted with and equal part water. Within 10 days all that will be left is a small bald spot.
If you really need it to go away sooner a tetracycline (not oxytetracycline like in LA200) given every day for 5 days should hasten the process, but not without risk. The risk is that the abcess will dry up and leave a permanent knot there.
If you want to lance it, wait till it forms a softer spot and lance it there. No sense in lancing whilst its still hard as a rock, you won't get much out.