This can be a difficult problem to fix by yourself. Patients get things stuck inside themselves more often than most people might think.
Now if you have a tampon stuck inside, this is very common, and you should see your family doctor or gynecologist, and they can quickly and easily get it out.
Sometimes this happens during sexual experimentation, sometimes during sexual games, and sometimes just when people are trying to understand their bodies. The problem occurs when people insert things that can go all the way inside - then they become hard to retrieve! Unfortunately many items that end up inside are rounded and/or slippery and are hard to grab. A doctor can sometimes get a good look with a speculum (a plastic viewer that allows a look into the vagina) and can then grab the object with a tong-like instrument. Sometimes other techniques can be used. I once saw a patient with a small votive candle stuck inside her vagina - from playing around with her boyfriend. The way I finally got it to come out was by putting a gloved finger into her bottom and putting pressure from above the candle to move it to the opening of the vagina. Although this might sound painful, it was not - just embarrassing, I am sure.
Given that you are a minor, some doctors might not see you for this problem. If you have a Planned Parenthood near you, call them and tell them you need to get in for an exam as soon as possible. If you wish, you can ask to have a discussion about birth control. You do not need parental permission for this. If no Planned Parenthood, call your county health department and ask if they have a clinic for young women - these are usually staffed by women doctors or nurse practitioners, and they could help you out in a very non-stressful and non-judgmental manner.
And by the way - if this happened during sex games with a boyfriend - make sure you are using safe sex practices and get on birth control if you need it! Stay healthy!