I am not so sure I filed this right, but anyway, about 4 hours after a marathon jacking-off session I found my penis swollend on the upper part of the shaft when about to take a shower which freaked me out like crazy. It doesn't hurt, the bump, or whatever you want to call it is soft and it looks extremely grotesque. Is it an infection or is it just swollen? Urinating doesn't hurt (or erection)
Will it stay like this? Will I like die, or something? (ha-ha)
Please help because I am extremely worried.

How old are you?

Swallow your pride and see a doctor.

Does your hand have any diseases? Ha. Ha. I made a funny.

Did you use lube? Lotion? Anything? Is it a blister?

Ahhh, I'm like 17 and I don't want to see a doctor, because that's would be like super embarrassing, plus I'm under 18 and my parents would find out and they're super Catholic freaks. It's not a blister, it's a lump, sort of. This never really happened before and there is no way in hell it could be an infection because I am not sexually active and stuff. I didn't use any kind of moisturerizer but I usually do, and my was like red after the marathon... :/
(My hand was recently diagnosed with a bad case of handitis... that might be it.)
I'm pretty sure it is JUST swelling, if it is how can I treat it?

Over enthusiastic masturbation causes this.
Basically you have bruised your member.
It will recover in time. Just leave it alone.

God Bless you, Curlyben, I was about to have a heart attack... (ha. Ha.)
How long do you think I should give it?

48-72 hours especially as you where bashing the bishop for so long.

Woah that's long...
One more thing... I'm a swimmer and I have this competition thing tomorrow at school... Should I go or make up an excuse? I want to be back to normal asap. (in other words: Will swimming in a school pool influence it somehow?)

You have seriously abused your member, it will take some time to recover.

Actually, the swelling went down by like 250%. Yay.

If it is swollen or bumpy with no extreme pain and possibly just some irritation than it is nothing. I get that also if there is a rough period during sex where it gets bent or some sort of trauma. It will go away in at most a week or 10 days. Just avoid masturbation or sex during that time and wear loose clothing. It may not be possible if you are at work but when at least home, just wear loose pants or gym shorts minus the boxers etc so that there is no pressure on it. You'll be fine.