Very little. A chunk of lead such as a bullet, fishing sinker or wheel weight will mostly pass harmlessly and intact through the digestive tract (although, that wheel weight will certainly give you something to remember when you pass it).
Lead, in large quantities, finely divided (powder, fumes and dust), or over long periods of exposure will enter the body in quantities large enough to cause symptoms of toxicity. Those symptoms tend to be neurological such as tics, tremors, psychological problems and learning disabilities.
Lead compounds, especially those that are water soluble or soluble in (stomach) acid are far more dangerous than the metal because absorption is facilitated by the solubility. Some compounds that are used to make white paint pigment such as Lead (IV) acetate, also known as 'sugar of lead', are quite dangerous because they accumulate as dust and paint chips on the floor of residences that are painted with them. Young children are apt to carry the material to their mouths after getting it on their hands. Younger children are much more susceptible to lead poisoning and the resulting neurological damage than adults.
Nothing happens
you die
pain
You Die
you die...
I assume you mean Lead. If that is the case go to the hospital, lead is toxic and you may need to have your stomach pumped depending on the amount of lead you ingested. If your talking about pencil lead which is graphite then no harm will come and if you meant l.e.d. than again nothing.
If you swallow a small piece of mechanical pencil lead, it will likely pass through your digestive system without causing harm. However, swallowing a large amount or if it becomes stuck, it could cause a blockage or injury. It is recommended to seek medical attention if you have any concerns.
You can get chemical burns along your throat and stomach if you swallow lye.
You burp bubbles
It depends on how much you swallow. If it is a large amount, you could get diarrhea and/or vomit.
This too will pass.
Your ink drys out.