A little penis inside my vagina?

Most likely, it's just your cervix⁠ (cervix: The opening to the uterus, the bottom of which is at the back end of the vagina.) .

The cervix is the end of your uterus⁠ (uterus: An internal, muscular reproductive organ in the pelvis. During pregnancy, this is where a fetus will develop. The lining of a person’s uterus is also the thing that sheds every menstrual cycle in what we call a period.) , or the beginning, depending on how you look at it, and the cervix and cervical canal jut into the back of the vagina⁠ (vagina: The internal passage leading from the opening of the vulva to the cervix of the uterus.) . When you're not highly aroused ( arousal⁠ (arousal: A state of sexual excitement and interest that sends messages to the brain which create physical changes and sensations, such as increased blood pressure, erection, lubrication, loosening of the vaginal or anal muscles, and increased physical sensitivity.) usually will pull the cervix further back), you can usually feel it by placing your finger inside, and given that it is a bit tubular, and also has a small opening on the end, it's easy to see why you might think it resembles a penis⁠ (penis: One of the two external reproductive organs of people often assigned male at birth.) .

Next time you're at the gynecologist⁠ (gynecologist: (Pronounced guy-na-coll-o-jist) A doctor that specializes in the health of the uterus, ovaries, vagina, and vulva. . They may also be referred to as "OB/GYNs" or, informally, "gynos".) , you can even ask him or her to take out⁠ (out: Short for ‘out of the closet’. When someone’s LGBTQ+ identity is known to other people.) a mirror when they're doing your speculum exam so you can get a look at it: it's a pretty cool thing to do, and will likely clear things up for you.

For more on your sexual⁠ (sexual: About or relating in some way to sex or sexuality.) anatomy⁠ (anatomy: The body, parts of the body, or physical structure of organisms like people, animals or plants.) , have a look here: Innies and Outies: The Vagina, Clitoris, Uterus, and More.