I saw a lump under my armpit since like 2 weeks now. It is really tiny and I thought that it was nothing because it busted yesterday and it is a little painful when it is touched. I am only 15 and now I have signs of fever. I'm scared! What do I do?

Well sounds like from shaving under your arms, could be ingrown hair or even cellulitis. If it's hard it could be an abscess.

Sometimes you will get a pimple-like place in your armpit from soap, deodorant clogging your pores. You say that you ruptured it and it's a little painful, clean it well and it should heal in a few days. I don't think your fever has anything to do with it. If the area gets worse or your fever continues, see your doctor.

It could have been a cyst of some kind. A fever is a sign of infection. Some people have a normal body temperature of 100.8 but the majority of people are usually between 98 and 99 degrees.  If you have a fever you can take Tylenol for it. Try using a very warm (not hot) compress on it a couple of times a day to keep it opened and draining. If it continues to bother you, you may want to see a Doctor.

The other answer here is correct, this sounds most likely like a skin condition like an ingrown hair or even just a pimple caused by a blocked pore or something like that... Especially if you shave your armpits.

But if you are worried, the best thing to do would be to check with your doctor just in case. It is always better to be safe than sorry.